Your Mom has stage 4 ovarian cancer. I'm sorry. I have it too. My sister died from it. Once ascites (what they call the fluid they pulled out of her belly) begin, the average survival time is about 6 months depending on what kind of ovarian cancer, most likely high-grade serous carcinoma, which is what I have. She needs to be tested for BRCA1 and BRCA2 and SO DO YOU if she is positive. I'm a documented BRCA1 as was my late sister--and having a 1st degree relative with OVCA increases YOUR risk exponentially.
I'm sorry for this news. I know a lot about ovarian cysts but not much about ovarian cancer. It may be helpful for your mom to get a copy of her pathology report. It would be helpful to do some research about ovarian cancer before her oncologist appointment as it will help you know what questions to ask. Maybe someone else will come along with some words of wisdom.
I wish the best for your mom. Let us know how the appointment goes.