It doesn't sound childish, it sounds like flirting and some sexual touching. But it sounds like while you would like to have her be your girlfriend because you have strong feelings for her, she's not as into you - she seems like she just kinda wants to play around with you. Because otherwise she would not have told you that she doesn't like you three times. On the other hand, you were also lying to her when you said that you only wanted sex, so it's possible she was trying to protect herself too. I guess in the future, I would be a little more honest - you don't have to tell someone that you have strong feelings for them, but I also wouldn't say that you only want sex, because that will confuse someone who DOES like you more than that, and might even cause them to cover up their true feelings. With this girl, if you really want to, you could ask her out on an actual date, just in case she really does like you more than her words suggest, but I would just proceed with emotional caution, because she already told you she doesn't like you, so this might not work out. But again, it might be worth a shot, since perhaps she was only hiding her feelings since you were too. And I guess what do you have to lose?