How to care for someone with frequent UTIs?

A couple of years ago, my grandma went into the hospital because she needed a pacemaker. She kept losing consciousness. While in the hospital she required help going to and from the bathroom. The night before her surgery, she paged a nurse for help, but 15 minutes went by and no nurse. She decided to go to the bathroom alone. Her heart stopped for a moment, she lost consciousness and fell. The nurses, upon finding her, shoved her against the wall and demanded she stand up. She couldn’t. She had broken her neck and has been unable to walk or stand since. I care for her full time. She has frequent UTIs. Her doctor says this is because she is incontinent and is unable to fully empty her bladder. I changed her often. I wipe front to back. I encourage her to drink water (she’s stubborn). I give her cranberry pills. Still she gets a UTI every few months. What can I do?