Ascites

My mum has stage 4 colon cancer. She's been receiving blood transfusions as the chemo was so brutal and seemed to strip her of everything. The chemo didn't work anyway and she's had her first lot of immunotherapy a couple of weeks ago.

in the last week or so though she's swelling up! Her feet are like giant Cornish pasties and her belly is so swollen and taut. She went to hospital appointment and they've said it's not a blood transfusion causing this but the cancer.

obviously I've googled and the first thing that came up is that ascites is probably a sign that the end is near. And then that this is the end stage, which was horrifying.  Is this true? Or just horror stories? She's been quite poorly as in tired and bloated but she feels fine apart from all this water she's lugging about inside. 
 

I'm trying to balance between positive and despair here but I don't know much about this - can anyone tell me honestly what this might mean? Is it a sign of cancer advancing? She will be given an appointment to drain s and scan when they have one but nothing yet.  Could it be anything to do with immunotherapy?