I can understand that this can be distressing. Postmenopausal state itself can predispose to this. Has she had scans to look for any kidney stones ? Does she have any problems with urine flow like incontinence?. Has she got any herniation like cystocele ? Is she having any residual urine in bladder after voiding ? These are few of the things an Urologist will look into. What's her creatinine ? Urologist/ Nephrologist will be able to advice remedies like liberal fluid intake, antibiotic prophylaxis, cranberry juice (warning- can increase calorie and sugar intake, heartburn), any interventions if there are anatomical abnormalities. Please take your mum to a urologist/ Nephrologist. Hope she feels well soon.