Why does my mom keep getting up through the night and walking around her bedroom?

I do that myself. The reason is RLS.

my Dad did this too. While he could not express wha he was feeling...I am pretty sure he also had it.

it is a neurological disorder. Hard to describe, but the only relief is to get up and move. This usually effects people between bed time and 3-4am. This is why it is called a sleep disorder even though it effects legs and sometimes arms too.

It can be caused by a reaction to certain meds, but for most it is inherited. there is no cure. Sometimes a bar of soap in the bed actually helps. Most every placebo works too...for a short time. Mostly, I find, if I keep moving the worst of the sensations can be held off.

Anxiety perhaps.
Wandering is a common problem with dementia. You might want to look that up. I’m not sure if this is considered wandering but keep a close eye that she doesn’t leave the home.

ohh gosh.. I shadowed my mom all night long.. went to her home which was close to mine... stay with her all night only to find out I had to shadow her.. get home so hub can go to work and I would get our kid ready for school and repeat. After awhile hubby noticed I was sleep deprived... You may want to ask about serequel, or other sleep aid. Then you have the risk of falling...
Anyway, you can get bars on her bed to kinda lock her in so she doesn't wander? Does she have a UTI ? doesn't sound like it... sometimes the internal clock goes awry... ]
have you tried melatonin? you could ask about ambien,, but then again... fall factor.
ask doctor about"sundowner syndrome" maybe get her walking more in afternoon before bed or near bedtime...
look at her diet..perhaps she needs something more or less before bed? no sugar or caffeine.
"NATURAL CALM" its magnesium supplement to help sleep... look it up..
covid around,, other remedies may not be appropriate at this time..
good luck.
stope feeding her or giving her liquids and hour before sleep,,, i heard somewhere.