This is Dr. David. I am reviewing your question now and will be with you momentarily.
I am sorry your mum has been suffering so much from urinary tract infections and fistulas
she may benefit from vaginal estrogen creams which can help improve the muscles of the vagina and vulvar area and could help
she should be doing kegel exercises which can help strengthen her pelvic floor muscles. has she tried doing kegel exercises?
she can ask her doctors about medications like Neurontin (gabapentin) or lyrica (pregabalin) which can help decrease nerve pain in the pelvis from her prior surgery. is she on these mediations?
she should make sure she drinks lots of water and cranberry juice. this will cause her to have to urinate more frequently, but she needs to drink more to prevent bladder infections
let me know if you have questions.