I don't want to help my mil after she donates a kidney
Why don't you want to help your mil?
I feel like she just sees me as a piggy bank.
If that's how you feel, I think it's something you should set aside for now. She is in the hospital and recovering, so she needs everyone to set aside their differences to help her.
On second thought I don't think she's really trying to take advantage of me. She's just trying to show her love in her own way.
If you mother in law needs your help and approaches you with sincerity, then you should see what you can do to assist her. Listen to her needs and if they are reasonable, see what you can do to help her out.