As a temporary introduction to getting clean every day, how about cleansing foam and shampoo caps. This will start the process
I add some links but I do not work for this company but I use these products when needed
www.completecareshop.co.uk/personal-care/aids-for-hair-washing/no-rinse-shampoo-cap
www.completecareshop.co.uk/continence-care/incontinence-wipes/vernacare-senset-cleansing-foam-case-of-12
Help her wash one part at a time so say top half, the cardigan etc has to come off for this, one arm at a time, don't wash arm and let her put back in, have clean clothes out of sight and cardigan etc will go straight into the washing machine and on before she can anything about it.
The cat will still recognise her to come to sit on her
With the foam which can be easier to introduce than water and clean clothes, if doing this in the bedroom make sure it's warm, curtains closed, and if needed, strip the bed so no chance to get back in under the safety of sheets.
It's hard for you and to be totally honest I still struggle a lot with self-care due to many years of heavy doses of antipsychotics and not caring about myself at all, I've started trying to care due to a thread on here.
If the food is encrusted, I going to guess it's coming down her front, these may help as coordination can be affected when heavily under the influence of antipsychotics, most of my food used to end up on my clothes and I couldn't have cared less. I dropped a pea yesterday which rolled off my plate, that upset me slightly but looking back dinners were all over my clothes and it didn't bother me.
When my co-ordination is poor due to a neurological condition I have, I use these www.completecareshop.co.uk/drinking-aids/bibs-for-the-elderly/disposable-bibs-pack-of-125-view-large?gclid=Cj0KCQiAn4PkBRCDARIsAGHmH3ekNLdDA_vYYAFbEWRoQsNIfb40mz2vaSykdJb2oPzB4Q6q0uSCK7saAkvwEALw_wcB