Hi Omega1!
You already have an answer to your first question:
because she's worried she'll forget.
This might not be the only reason, but it's as good a reason as any, because her motivations are secondary here.
The important part right now is, that you don't feel comfortable anymore with doing stuff for her that she could and should take care of herself.
Correct me if I'm wrong, but I assume that this dynamic has been present in your relationship for quite some time. So it's no surprise that she gets upset when you suddently don't want to play along anymore. Still, this is something that bothers you so it's fine that you want to adress it and make a change.
To accomplish that, I think it's important to first establish a set of 'rules' for yourself: In which situations do you want her to take care of things on her own? On which occasions is your help really needed?
It's essential to make a clear distinction between these events, so that you can act consistently and still be supportive when your support is really needed.
If you got that covered you can think about how to communicate those rules to her, without stirring up unneccesary conflict.
Can you think of a communication tool that might be helpful here?