Baby shower 😞 drama

Can use some opinions.. My bf's sisters decided to plan a baby shower for me without me asking .. They have a big family so majority of pp there will be his family since I have few that live near & will go. Anyway his sister is asking for my mother to contribute $ for the party and ofcourse my mother doesnt want to (she contributed to my first bb shower) & doesnt work so she really cant contribute. Idk what to tell these pp or what to do. I feel trapped in the middle & its stressing me out .. Any opinions are welcome