Is it permissible for a Muslim woman to sever ties with her mother who abandoned her, or is that considered forbidden?

Under no circumstances is it permissible to sever ties with one's mother, even if she has wronged her child. Disobeying parents is not excused by their wrongdoing or their shortcomings towards their child. One must strive to maintain ties with one's mother, be dutiful towards her, and repent to Allah.