My Mom is incontinent and refuses to wear protective undergarments. She has accidents in other peoples homes and public places. She refuses new clothing although hers is old and worn. She refuses offers for hair and nail treatments. Very frustrating as they have financial resources and my Dad is very active and supportive. We have tried everything we can think of. She has not had any definitive diagnosis.
There is a difference between fecal incontinece and full bowel incontinence; I only found this out when I sat down with her and her new geriatrics doc and explained what was happening.
There was a solution; I'm not saying that there will be a solution beyond Depends for your mom, but her doc NEEDS to know what is going on.
Remove all her regular underwear from her drawer. Replace it with a Pull-Up type incontinent type brief.
If she asks where her other underwear is tell her that it is all in the wash. It is torn, you are getting new underwear.
When she takes off clothing that is torn, stained put it in a "rag bag" and replace it with a newer item. As these get used replace them as well. (I used to "argue" with my Husband about old t-shirts he would tell me the new ones were "for good" and the stained, torn ones he wold wear around the house. I just started tossing the old "yukky" ones)
Unless she really has a problem with nails and hair I would not push it to get them done. A hair trim once in a while is nice but if she feels unsteady getting into some of the salon chairs ask if she can sit in a regular one. (My Husband had a terrible time with the chairs that turned on him as he tried to sit, the leg/foot rest was in the way and trying to get him to sit safely while backing the walker to the chair was nerve wracking)
As far as the nails go, if you can do the cutting and shaping at home that should be good, for the feet a trip to a podiatrist will take care of that, and it is a good way to get her feet checked anyway. (Medicare covers podiatrist for nails)
With most of these things pick your battles. The most important one here is the incontinence. And this is medical and should be checked out. If she does not have a Dr. appointment scheduled soon I would make and appointment. And she may not even realize what is occurring if her sense of smell is not good.
(I am the last one to stress about old clothes while some of mine are in good condition I have a few flannel shirts that were my Husbands that I wear just to have him near me and one of them has a tag in it with a date of 1996)
And if your Mom was never one to visit a hair salon or have her nails done there is no reason to do so now. You can easily trim her hair and do her nails. Call it a "Spa Day" You can even have an Aid come in to do just that once a month. Or if there is a problem with Mom bathing you could have an aid come in 1 or 2 times week.