why wont my friend follow me back on instagram?

[loudsweater726]

Well we are sort of friends. she has more followers than me (because I got my account 2 days ago), but she is following wayyy more people than she has followers. I requested to follow her, and she accepted, but she's not following me back. idk why!!? so then I unfollowed her and then requested her again so that maybe she would notice that its me, but she accepted and didn't request to follow me back... again. I think its kind of dumb. and I don't really care about her photos.
Is it really rude to just unfollow people? (life if you are unfollowed, do you get upset?)
And also, should I try talking to her about following me back (and if so, what should I say), or should I just unfollow her? I really do want more followers...