How do I get my 92 yr old mom to accept help and deal with incontinence issues?

I currently live with my 92 year old mother and have a daily round trip commute for work in excess of 150 miles. Until the last six months she was very independent with relatively few health issues and I worked much closer to home. She is still healthy but dealing with mobility and incontinence issues (both bladder and bowel). She tries to hide it and/or clean it up herself and I find the evidence when I get home after being gone in excess of 12 hours or more. My sisters help out with appointments and errands but have only been coming to spot clean the house about once a week. Needless to say the bathroom and carpets need daily care. I am looking for suggestions and advice but am also venting. I just ended the day arguing with mom about wearing adult diapers if she cannot make it the bathroom in time and of course she doesn't want to. Not only that but she often goes without underwear all day and finally admitted it, says it gets in the way. I cannot recall the last time the woman took a bath and don't think she sponge cleans often even though she claims to. I am trying to be tactful and respectful of her dignity but this is grossing me out. Not what I want to come home to after being on the road for a couple of hours.