Although Kat and Baptista are blood related, actions speak louder than words. Behaviour is stronger than just the idea of being blood related. To feel like family and be appreciated it is all done by behaviour. Baptista behaves very differently towards Bianca, which is not fair to Kat.
You are allowed to terminate your relationship with toxic family members. You are allowed to walk away from people who hurt you. You are allowed to be angry & selfish & unforgiving & don't owe anyone an explanation for taking care of you.