AH, now that is useful, it's given me a list of possible foods, thank you.My mother in law suffers with this - have you tried a low-FODMAP diet? It's the only thing that works for her!
Also stress really doesn't help - I know it's not always easy but try looking into some methods of lowering stress if you do experience it.
According to NHS advice I don't need to call my GP at this stage, my condition lasts about 3 days and isn't as severe as your Mother's.My mum suffers with this and had a bad flare up a month or so ago and was admitted to hospital for the night. Turns out she needed antibiotics for this particular flare up as it was infected. Might be worth giving your gp a call?
Any kind of seeds are nasty, I eat loads of grapes thankfully seedless and I do avoid fresh tomatoes.Stress is a huge factor and so are seeds in tomatoes.