My Mothers has started talking out loud during her naps as if she was dreaming. It's very wierd. Sure she's got early Dementia but even on her good days (knowing the date, time, place, etc.) she's been talking out about others that are nowhere near us. She's so disoriented on these days. I reassure her as much as I can once she's awake but scratch my head about how to handle it better. Any ideas or is this just another chapter during her journey?
If she develops night terrors, sleep walking, or starts acting out her dreams by moving her arms and legs, that may need some treatment, but just talking isn't, apparently, significant. (And you don't have to have dementia for it to happen!)
Unless you mother starts to have terrors, I wouldn't worry too much. If her dreams become too stressful, you can talk with her doctor about them. He/she may be able to prescribe something to calm her if she needs it.
My Mom laughs and babbles in her sleep, I think she has invisible company sometimes. As long as she is happy, go with it. Good luck