*Sigh* She is not houstrained yet because you took her 4 weeks too early from her mom, who would have started to teach her things like that, and she likes to bite not only because that's what puppies do, but again, she was taken too early from littermates and did not learn that it was a bad idea.
I have a Shiba Inu, she is almost 3 now. I got her at 10 weeks and she took exactly 3 days to housetrain permanently. They are very intelligent and independent, but she was taken too early to learn a lot of things. When she bites, yelp in a high pitched voice...it mimics her littermates, because that is what they do to learn bite inhibition. If/when she stops, praise her and give her a chew toy since she is "in that mood". When she is not, play again. I did this with Saki for a few weeks and she hasn't bitten since.
So you got her at the end of February which makes her what, 16 weeks now? 4 months old? Of course she isn't trained yet (unless you are strictly speaking about HOUSEtraining, in which case, ignore that, but what I will say next does apply)! It takes months to train puppies and at least a year to train an independent dog like the Shiba that they cannot do what they please, plus lifetime training to make sure they don't revert back to a bad habit.
Shibas are really bright dogs - you simply got her from her mom way too soon. Good luck with her and please, next time, walk the other way if someone wants to sell you a Shiba (or any puppy) at 6 weeks of age. They shouldn't ever leave until at least 8 weeks at the minimum - 10-12 weeks is better.
I really hope I didn't sound harsh...but I know this breed inside and out and love my own dearly and they are NOT a breed for someone who doesn't want to do research or constant training. Really, good luck with yours.
I will tell you though, if it's any consolation, that they DO settle down around the 2-2.5 year age range. :-)