This question is about my mom (60). she usually gets 6-7 hours of sleep,& thats not enough for her. this caused expected memory problems. except earlier, she forgot a short conversation with my brother. is this also possible, or is it something else?

It is difficult to assess anything from your post. The quantity of deep restorative sleep needed to function well differs at different ages, but undiagnosed sleep apnea often goes unrecognized for years. With sleep apnea you can be down for 12 hours but only get a small fraction of this in deep sleep. This causes similar symptoms. She needs a good checkup and maybe a sleep study.

Not feasible to be precise but suggest neurological consultation to screen for dementia such as Alzheimer’s. Lack of sleep may not be the full answer