Mom has suddenly lost the ability to do some things, but on the other hand walks much better. Any meaning to it?

My Husband would lose the ability to do something seemingly over night.
This is why I suspected he also has Vascular Dementia as well as the diagnosed Alzheimer's. Often a doctor will diagnose Alzheimer's and do no further testing so I think may forms of dementia are misdiagnosed.
Little mini strokes can cause one to loose the ability to do something rapidly rather than the slower decline that Alzheimer's typically has.
Work with your mom re-teaching her things like hand washing she may not retain it or loose it again.
And it could also be the mystery of dementia...ya just never know! Every day can be a surprise.
My Husband was doing a lot of things that he should not have been able to do and lost the ability to do things he should have been able to so.

I would bring this to her Drs attention and the weight loss. This could be the desease and it could be another problem.

My sister is doing exactly the same with the exception of a straw. She is glad to see me but does not call me by name or by our relationship-she had told staff this is my sister-now does not. Word confusion getting worse, still having hallucinations, walking is really strong in the forward mode-back sometimes good sometimes not. Yes, she knows a straw-helps her to get to the bottom of a drink vs tipping at an angle to get the last drop. She could play a simple card game-not so much in just a week. Maybe having a bad day-she seemed more tired than usual. She has lost approximately a pound a week in the 5 months she has lived at this unfortunate facility-lazy staff and bad food. I always have a juice drink or protein shake in my purse for sis. Crying gotten worse-I would say was whimpering for a minute or two when she first sees me-happy tears??-now volume is louder and lasts longer-another reason a community would not take sis-says this is disruptive behavior. Says she misses me and wants to be with me. We have one more facility to try-about 5 mins away. -out of 20 or so up to now. I am praying they will accept my sister. Typically these types of changes are not a good sign for us-been a downhill slide almost non stop.

Tredandweary: what a great way of describing it! Made me laugh out loud but so true!

Probably just part of the wonderful mystery of dementia. I think it can be compared to a box of cheap chocolates. Instead of the good pieces, it is filled with the ones you don't like. Once in a while you can find a good one, but mostly all are some weird jelly concoction.