Mom lives in independent/ AL, is moderate stage Alzheimer's and Vascular, and recently stopped getting in the shower. What's next?

I’m glad she’s adjusting well to the new AL! That’s half the battle. You say she eats well when you’re there...what is the feedback from the staff about her eating when you’re not there? I know in Moms NH they have to keep track of the % each resident eats and drinks at all meals. You should ask either the nurses or the dietician if they keep similar records.

Does her AL fee include help with showering or is she on her own for that? What does she say about showering? Is she afraid? Or doesn’t think she needs to? At least she is washing up in the sink, so she must still have some desire for cleanliness. That’s good. If you can stress the importance to wash her “ladyparts” thoroughly each day, she may be able to hold off UTIs. Especially if she is starting to be incontinent.

I knows it’s so hard to be a spectator to their decline. I visit mom every day in the NH and can document the things she can do one week that may be out of her ability or interest the next week. Heartbreaking. The best we can do is advocate for them, and try to be realistic. I found I was slow to accept her decline, and could have been more accepting/forgiving/helpful if I had removed my blinders earlier.

There are a lot of steps to taking a shower if you really think about it.
There is also the possibility that she is afraid.
Afraid that she will slip, afraid she will "do something wrong" afraid of the noise. I was told by a Physical Therapist that the head and torso are vulnerable spots and the water hitting that area is frightening to some.
So there is a lot going on in the shower.
She may need some help with showering.
If getting an aid is a possibility that might help. Even if it is just someone there to be sure that nothing happens. But a trained aid can get even the most resistant person into a shower. It may take time but the job will get done. (It may take a few visits to build trust but it will happen.
The other option since you think she will be going to Memory Care fairly soon would be to place here there as soon as possible so she can get used to her surroundings while she is more able to.

It sounds as though the shower issue might have happened at the same time as she moved into AL. Does she recognise everything in the shower? For example, do they have a mixer tap instead of two taps, or vice versa? If she has tried and only got cold water, she might have decided that it doesn't work.

It certainly sounds as though she may be declining faster than normal. This may be the best thing for her and for you, though that may be hard to accept so quickly. It's great that she is actually happy!