My Mom (92) with dementia often talks about her job, but she has not worked in a years. Should we remind her she doesn't work anymore?

I agree with GardenArtist above, do not remind your Mom that she doesn't have her job. If talking about her job makes her happy, that is the main thing. Just go along with it.

My Mom [97] is in long-term care but she thinks she is at a motel, so we just let her believe that. Sometimes one has to fib with an elder with dementia. My Mom wants to get out of her wheelchair, but I tell her she can't because she hurt her foot [which she didn't, she just can't stand up any more] and she is happy with that explanation.

No, no, no. With dementia, she won't realize that she's not making accurate statements and correction will only upset her, as she may feel challenged. Instead, ask her to tell you about her job, what she liked, what she did, people with whom she worked. Play into her reminisces and help make them positive experiences for her during this stage of her life.