I know of people at Duke University in NC, and also UNC chapel Hill. Look for the dept of OB/Gyn, division of urogynecology at either of those places. Ask to be seen by a Urogynecologist there.
For recurrent UTI there should be a workup to look for kidney/bladder stones, or problems with bladder emptying (also called urinary retention). If those workups are negative, look for evidence of fistulas (abnormal connections between urinary system and vagina, or bowels- these would be possible if she had radiation therapy or prior surgery in the area). If the entire workup is negative for anomalies, then many providers will start her on a 3-6 month course of a daily antibiotic, after treating and clearing the current infection. After 3-6 months of chronic therapy, they would stop the antibiotic, and see if the infection stays away.
E. Coli is a bacteria that grows in the GI tract of most humans. Sometimes it can also colonize the vagina and lead to UTI. so your mom is not unisual in that she has E. Coli in her GI tract. If UTI is untreated, it can sometimes track up to the kidney causing pyelonephritis, which can also be life threatening. So, they need to be treated.