My mother is seeing people and talking to them, but there’s nobody there. Any advice?

Don't assume that there is nobody there just because you cannot see them.

I’m sorry, I’m sure this is very scary for you. I went through similar phases with my mom and I dont think there is anything more upsetting for me than to see her in that condition. There were a few causes that we found that may give you some ideas to follow up on.

First and easiest, have her checked for a UTI. Mom always hallucinates when she has one. You could give her a simple AZO test at home just for a quick indication, but then take her to her doctor or urgent care for a professional test and prescription if needed.
Also review her medications and their interactions. You can read the info that comes with her drugs, look them up on webMD, or ask a pharmacist. One of Moms drugs also could cause hallucinations, and discontinuing that one helped eliminate that as a cause. Also an interaction problem had us discontinue another one.
Thirdly, have her eyes checked. Mom had an optic nerve stroke which left her with a very small area of peripheral vision but nothing else. She sometimes cannot distinguish what’s she’s seeing. Sometimes she thinks that her closet door is a person, until I correct her. So if she’s having vision problems along with dementia it might be very confusing for her.
I hope you find some more help with other posters comments.

This is the Dementia. If she isn't frightened, then I wouldn't worry about it. If she is contact her Dr. There is medication for it. My Mom always saw a little girl.

Have you talked to her doctor about this?

Has she started a new medication, rxd or otc?

Has she been checked for a uti?

There are many causes of hallucinations and some are treatable and some not.

Rule out any treatable causes 1st, with the aid of her dr or pharmacist.

I am not trying to freak you out but people will see others when they are preparing to pass, this could be what's happening. If she's not afraid and there is no cause, don't worry. Babies and small ones usually bring joy and happiness to people, I hope it is to her.

My Mom went through a period of seeing elephants and tigers walking through the rooms in her house, and seeing people knitting in her back room with their cats. When I asked her she said she wasn't scared of other beings in her house. She did keep her cat out of that room because he didn't like other cats. She was living alone after my Dad passed, not sure what your Mom's circumstances are. My Mom now has been diagnosed with dementia, not sure if the "visions" were a precursor to that. She only had those types of sightings for awhile.