Any ideas on a method mom can use to bathe herself and be safe?

I have the opposite from what I've read so far. My mother suffered a stroke and has limited mobility of her right side of her body. My sister in law and I share giving my mother a shower 6 days a week in the morning. But my mother feels she needs a second bath in the afternoon when we are not there to help her. My father is in the home and is her main caregiver but because of his physical limitations he is unable to help her. My mother will walk into the restroom stand over the sink and scrub herself with her good hand with no support. My concern is her safety when we are not there to assist her. I have tried to talk with her and try to convince her one shower a day is enough but with no luck she continues to do it on her own. If anyone has any ideas on a method she can use or a device we can buy to help her scrub herself and be safe.