Did I understand the situation correctly....there were abnormal cells in the urine, but CIS was NOT found during the TURB ("scraping/biopsy")?
IF THIS IS THE CASE, I would suggest that you seek a second opinion at a place that sees a LOT of bladder cancer cases. Urine cytology tests are notorious for being VERY sensitive...that is that they do find cancer, but they also "find" it when it is not there. They usually indicate that further tests, for example, the TURB be done to confirm that cancer is indeed there.
If CIS is present, it is a high grade cancer and needs treatment. But especially in your mother's case you would want to be sure that it is present. So, again, if the only diagnostic test that was positive was urine cytology, I would urge you to get a second opinion ASAP. If CIS showed up in any other way, from a tissue biopsy, than yes, BCG is the only option.
Sara Anne