I will give you an answer from the Islamic view point, I'm assuming you take your religion seriously and believe in Allah and the day of judgment as well as hell and heaven. I hope that it will be of assistance to you.
1. First of all, I must say that I'm not sure what you mean by western as you didn't specify, do you mean take of the headscarf? Do you mean wearing jeans (which is tight clothing)? What do you mean basically is what I'm asking. A t-shirt and shorts? I have no idea what "western" means.
2. With regards to the hijab. The hijab, as per the Noble Quran and Sunnah, is a head scarf that covers all of your hair (not showing any of it, some women show the top part), the headscarf should be drawn over the bosoms (some women draw it behind their back and expose their bosoms), and it should cover the ears (some women wear hats and call it hijab). The hijab also covers the entire body except the hands and face, although the majority of Islamic scholars state covering the face (niqab) is obligatory, but there are some Islamic scholars that say it is Sunnah for extra reward. The hijab is also a dress that doesn't show the texture of your body as you said, nothing tight showing the body, and the hijab is not colorful drawing attention to you (thus defeating the purpose).
So this is the hijab, anything less than this is sinful, and every sin in Islam weakens faith. The Prophet Muhammad (s) mentioned that when a person sins, a black spot appears on their heart, and if they keep sinning, then the darkness will spread until the heart is submerged in darkness (having severely weak faith), and if the person continues, then Allah will seal their heart (thus good deeds become much more difficult to do, and thus you cannot earn as much reward), then if they still continue, then Allah will stamp it, and they will become disbelievers. The Islamic scholars say that the seal is worse than the submersion, and the lock (stamp) is worse than the seal, as at that point it'll be incredibly difficult to return back to Islam.
Hence Allah says:
And be not like those who forgot Allah , so He made them forget themselves. Those are the defiantly disobedient. (59:19 - Noble Quran)
"Forgetting Allah" means to sin habitually, such as not wearing hijab, disobeying parents, delaying salat, etc. "forget themselves" means Allah will misguide them as they chose to ignore his signs and sin habitually, and this is how the apostates forget that they were Muslim (metaphorically).
Likewise, Allah punishes sins in this life with hardships, so every sin makes life harder for you, as Allah says:
What comes to you of good is from Allah , but what comes to you of evil, [O man], is from yourself. And We have sent you, [O Muhammad], to the people as a messenger, and sufficient is Allah as Witness. (4:79 - Noble Quran)
So Allah says here, that if evil touches you, it is from yourself due to your sins, and you did not repent, so Allah is causing you distress/hardship to wipe away the sins, so that on the day of judgment you will come to him sinless Inshallah and avoid the greater more severe punishments on the day of judgment, in the grave, and hell fire.
So sin DOES have penalty in Islam. Good deeds on the other hand, make life easier. The Prophet (s) said that everyone has a predestined place in hell and heaven and your actions drive you to one or the other, if you are headed to paradise, but are lacking good deeds to reach the high level predestined for you, then Allah will introduce hardship into your life to help you reach it through patience.
In Islam there are two good deeds mentioned that Allah will for sure reward without measure, and those two good deeds are fasting and patience. All good deeds, Allah multiplies by 10-700, but fasting and patience (in observing commands, avoiding sins, patience in hardships, etc) will be rewarded more than 700 personally by Allah on the day of judgment, and Allah knows best what his reward is, only that the Messenger (s) said that when those who lived in ease see the reward of those who suffered on the day of judgment, they will wish their skins were cut by scissors.
We believe in multiple heavens in Islam, one on top of each other with the highest being Jannahtul Firdous, the higher you go the more enjoyable it will be, and you will desire what you earn, and you want to earn a high rank in paradise so as to enjoy it more, and the way to do that is to sin less and do more good. Every good deed increases faith and wipes away the blackspots on the heart and creates white spots on it, polishing it.
So this is how the system of Allah works. Everyone will get what they earn.
2. With that said, using your friends who have weaker faith than you as an excuse to sin by imitating the kuffar, which is forbidden in Islam, is not an acceptable excuse.
It was narrated that ‘Abd-Allaah ibn ‘Umar said: The Prophet (peace and blessings of Allaah be upon him) said: “Whoever imitates a people is one of them.” Narrated by Abu Dawood, 3512; classed as saheeh by al-Albaani in Irwa’ al-Ghaleel, 2691.
So it is forbidden to imitate disbelievers, or as you call them westerners (as most westerners are disbelievers). The evidence here is the sahih hadith above.
If your friends who call themselves Muslim started drinking alcohol, fornicating, and worshiping idols; would you do the same? No you wouldn't, so why would it be okay to dress like them if they are doing something that goes against Islam?
Picture yourself on the day of judgment, a day that is going to last 50 thousand years, and of which Allah is going to bring the sun 1 mile between the people before judgment as punishment, and people will sweat according to their sins, and the only shade on that day is with Allah. Picture when the judgment itself actually starts, as Allah is going to judge everyone at the same time individually, your judgment might last hundreds of years, and when Allah asks you, why did you disobey your parents when they ordered you to do good, and why did you wear such and such clothing.
You're telling me that you're going to tell Allah that it's because your friends wore it and that you didn't deviate much from the hijab? Listen, if you think that's an acceptable excuse on the day of Horror, then by all means go ahead, if you think that you can say that straight to Allah, then go ahead, you are fearless, one of the most fearless people I have ever met in my life if you think that'll work.
But rationally, we know this is not an acceptable excuse. You are a lioness, these friends are like gazelles. Naturally a lioness among gazelles is going to stand out, and they might be scared or jealous of you, Allahu alim.
3. With that said, Allah's Messenger (s) warned people to be careful who they take as close friends, because people follow what their close friends do. If these Muslim friends are enjoining evil on you, or encouraging you to do evil, then you need to drop them. YOu should advise them first, remind them of Allah, but if they don't take heed, drop them. Whatever you give up for the sake of Allah, he will replace with something better, such as better friends who will be at your level of faith, and you can meet them at the masjid, I encourage you to get better acquainted with your community, go to the mosque and meet some more Muslim women, good Muslim women.
4. So my advice to you is, Obey your parents, they're not ordering you to do anything bad, and wear the hijab fully with the headscarf, enjoin good and forbid evil on your friends by reminding them of Allah, and get new friends who will keep your faith steady and increase it. Allah's Messenger (s) said obedience to parents is the second best good deed in Islam behind prayer on time, and the third best is jihad according to one hadith. So there is a lot of reward in it, don't let that reward leave your hands.