I think you've got to make it clear that you're not taking sides when these things come up and you're not available for loans or cash gifts. See who still wants to keep up a relationship with you once that's clear and keep up your family relationships with them. Try to keep in touch with your neice. When she's older, have direct communication with her if you can, and if you're in a position to help her get into college, apply for scholarships, etc - help her out.

Op. Here. Well I've talked with my family but no one has brought up the drama that has been occurring since the weekend. So far so good

Try to have minimal contact with family or cut the contact depending on your situation. My dad's family(my parents divorced) was financially messed. They kept asking me to help paying the bill and also stole my money, jewelry. I felt guilty for not helping them so my best decision was to move away and cut the contact with them completely.
Good luck OP

I had to completely cut off contact with my family for several years because I just couldn't handle all their drama and get my own life in order. Now that I am older and have a relatively stable life, I've resumed contact with several family members but keep a comfortable distance and show zero interest when they start talking about family drama. I still stay away from the most toxic people.

I don't know that cutting off contact was the best solution but it was the only thing that worked for me as I came from a background full of chaos and was dealing with enough issues of my own that I just didn't have the emotional energy to deal with them.