Maybe she taught you some things, but she didn't change you. You changed you.
You may have done he things you didn't want to do because you wanted to be "good enough" for her and didn't want her to leave.
Some of the changes, like quitting smoking, were clearly for the good. You did that hard work, even if she encouraged you to do it, and I hope you don't lose sight of that.
For the things you may not have wanted to do and may not see as good changes, like cutting your hair, this may be an opportunity to learn to say no, to have boundaries in the future, and find someone who likes you just as you are.
Why would she try to change me so much? I understand smoking is a bad habit but why the drastic change needing to be made. And why did I actually do it?
Why? We can all speculate why, but only she can say why she did it. Maybe she was trying to push you until you rejected her or maybe her attempts to control you were way she was trying to escape her own emotions. Maybe she was trying to change you into the person she hope you could be forgetting who you actually are, maybe she has a personality disorder that makes her a little bit chaotic. There are probably numerous other possible explanations.
Something that may help tease out for yourself why you did it is to ask yourself the question how would you have felt if she had asked you to do those things and you didn't do it?