82 year old grandma diagnosed with glioblastoma

I’m not sure if this is the right place to post this, since I’m new here, but I also thought I should post it here because I’m new here if that makes sense?

Just over a year ago, my then 82 (now 83) year old grandma was diagnosed with a glioblastoma. They said it was inoperable, and radiotherapy may just hinder her quality of life, so she opted not to have any treatment. She was given 3-4 months to live, but asked the doctors not to tell her. She also refused any follow up scans because she just wanted to be able to live the rest of her life free of worry.

She has been taking lionsmane and turkey tail mushrooms (the latter is an approved cancer treatment in Japan) and she’s almost entirely cut out sugar from her diet, as well as cooked fat - although I don’t really understand the benefit in that - and she also cut out meat for a while but we managed to convince her to reintroduce that since her diet was becoming so restrictive.

At the time of diagnosis, my mum was in the ICU with sepsis. My grandma presented with confusion, an inability to get her words out quite right or to find the right words, speaking in drawn out & tangential sentences (which isn’t like her at all), headaches, slight personality change, inability to do crosswords she previously completed with ease, and memory problems. She thought she’d had a ministroke triggered by stress, but when she got it checked out, the person doing her scan blurted out that she had a brain tumour, referred her to the neurological department, and she was diagnosed with a glioblastoma. Her tumour is located very near her pituitary gland which was why they couldn’t operate.

All this to say, over the last year, any symptoms she had have almost completely vanished, apart from the headaches. She’s doing crosswords more difficult than those she was doing before diagnosis. Doctors predicted she’d likely start rapidly declining within 6 weeks of diagnosis. I’m baffled, considering her age, prognosis, and lack of treatment, that she seems better than before she was diagnosed? I’m wondering whether possibly she was misdiagnosed? Although I’ve done some research and it seems as though different types of brain tumours are physically quite distinct, even if their symptoms are similar. The only other explanation I can think of is that the mushrooms are helping in a significant way, and I’m sure they do help, but I would never have imagined they could help to this extent.

Overall, I’m just quite confused and was wondering whether anyone has any insight to offer? She still refuses to get any follow up scans despite us suggesting that the doctors only tell us the results and not her. Anyway, thanks to anyone who bothered to read through my waffle & thanks also to anyone who responds :)