Post Op Questions

Regarding diet, firstly, does anyone have any advice? My Mum does eat quite a healthy diet, but are there foods that have to be avoided for a while/forever. I’m mainly thinking of the dairy issue. She has lost a lot of weight, and really needs to beef up some, especially if she needs to have follow up treatment.
Also, if she is advised to have chemo, will it be OK to wait till the end of July? She has an exhibition/sale of some of her art in Kefallonia the last week of July, and really does not want to miss it!!
I’m bound to have other questions, but will post them as they come!
Thanks for your support.