Why am I not enough for her?

That's quite a tale, Ember.  You seem to be quite anxious about this.  So the first thing I'd advise you to do is slow down.  Stop flitting around like a wild squirrel trying to bang its way out of a cage.  Be calm, and assess your situation.

There's no need to change anything about yourself immediately.  Before you consider any changes to yourself, you should ask yourself if this girl really knew the first thing about what she was saying when she "confessed her love".  It's likely she didn't.  Many people (maybe even MOST people) don't know the first thing about love.  They only recognize it AFTER the fact - then they say "Oh - I was in love!"  They only begin to understand a bit the second time around, in many cases.  And even then, there are those who can't ever figure out what is going on...what they are seeking, and what they are able to give.  So young people often assume that they're feeling love when they're feeling nothing of the sort.  So THAT'S your first consideration:  Does she know what she's talking about, or is she really feeling or expressing something else?

Given the very strong possibility that she doesn't know what she was talking about, the best play for you is to sit tight and basically return to how you were before you started thinking of the two of you as a couple.  Then see what she does.  She might bring the subject up again - in which case the two of you need to talk about any differences between what YOU thought she said and what SHE thought she was saying.  (All couples do this, in one form or another, sooner or later.)  If she doesn't re-approach the subject, you can assume she just figured out that she wasn't feeling what she thought she was.  In that case, you just go back to living your life like it used to be, before she ever happened.  Not to worry.  Something else will happen, soon enough.

Remember, if a person is attracted to you, they're interested in who they think you ARE - NOT in who you might turn yourself into for them.  They don't want you to become someone different, or behave differently.  So don't ever consider changing yourself in order to cling onto a relationship.  That's foolish.  Almost as foolish as starting a relationship with someone whose habits or personality you don't actually like, in the expectation that they will change them because of your influence. That's just Dumb, di-dumb-dummb!

there's plenty of fish in the sea you shouldn't let her treat you like that have some self respect and move on