I'm sorry to hear about your mom. You only get one. I was an oncology certified RN for 13 years. For whatever it's worth, you are doing the right thing just by being with her. Sometimes they can do a pleuradesis, where they inject a drug into the chest that causes the lung to scar on the outside, so it sticks to the chest wall. That gets rid of the space between the lung and the chest so the fluid can't accumulate. Problem is, if the fluid is accumulating that fast, it won't work. Plus, it's really painful, and the side effects can be fatal, just by themselves. Just be there for her, and with her. That's what you can do.