Has anyone dealt with vulva cancer can anyone advise how long we have?

Mum has vulva cancer she is 83 she had the same cancer when she was 38 and had a radical lumpectomy. She is in a lot of pain even though she Radical vulvectomy. She is now terminal in a lot of pain has 75mg fentanyl patch and oramorph. She is eating less th a 500 calories a day and very frail .Has anyone dealt with this kind of cancer can anyone advise how long we have , there are days when I think mum isn't going to last until the end of the week , now she is up and about at home.after spending weeks in bed, it I'd truly unsafe.