My mom has been up since 9:30am on Thursday. I've tried to get her to go to bed and she won't. Is this normal for people with dementia?

With dementia it’s super easy to gets days & nights confused. You have to keep them on a routine. My mother does still nap a good part of the day but goes on walks in the house usually during sundowner episodes. I’ve found that giving her .25 melatonin helps her to go to bed & sleep. It’s a natural med that doesn’t interfere with any of her other medications & isn’t too strong for her. Good luck. It takes a little practice to get it right but you can get them back to a correct day/night schedule.

Yes but there are meds that work!! As disease progresses and it does, meds need tweeking to keep up.
Blood work and meds....can't sleep all day either as some do, then roam all night.

Meds

Any sudden change is worthy of at least reporting to doctor, and taking in a urine sample or testing by dipstick (available OTC at pharmacy and ask pharmacist what would indicate reporting to doctor) to be certain there is no UTI.
Dementia often manifests in different ways at different times. It sounds as though she is getting more and more symptomatic, and the time you have left that you can care for her 24/7 may be limited.
Consider keeping a diary of her symptoms; this will help you keep track and help a doctor when you visit. You may require medications to regulate sleep patterns, but often they complicate things in that sleepiness can lead to falls. So can exhaustion.
Sorry you are going through this.

Staying awake for days isn't normal or common but its is something I've read here on the forum before, usually the people are manic so at least she's not that :(
Time to take her in for a check up, or at least consult with her doctor.