M.D.
My mom got cancer when I was in 10th grade, just before my dad was retiring from the Navy and we were set to move across the country. She is now 15 years cancer free.
People brought us meals, people helped get my siblings and I to and from activities, and people just came to talk to my mom. It really depends on what works for her. Sometimes just a NORMAL conversation might be all she wants.
I do agree that if you bring her food, ask what they like to eat. Don't just show up with a family favorite for you because they may not like it and then it just makes the night more difficult for them.
If you can help with some of the bills, by all means go for it. If not, you can't. I wouldn't be able to help another family pay their bills right now...but I would be able to give time, run errands, do chores, make meals, talk, etc.
So do what you can, but don't treat her like she has cancer...treat her like she is still the same person, because she is.