MIL is late 60s and we are very close. I see her usually once a week, or once every other week at least.
She came to ours for dinner on Tuesday night. BIL and SIL were also here, with 5 children also in total. She seemed quite spaced out at one point, and SIL asked me if everything was ok with her but I didn't really think anything of it (BIL and SIL live about 6 hours away so only see her a couple of times a year).
This morning I met MIL for a coffee. I was having a bad morning, and within the space of a few minutes she repeated the sentence "I would just write-off this morning if I were you" about four or five times. A bit later on we were having a conversation about her ex (my FIL - separated when DH was a baby) and she told me a funny anecdote about how he reacted once when DH was sick as a baby. I laughed and told her a similar story about how FIL had been with my DS when he was poorly a few weeks back, and she responded to this by telling me the exact same anecdote that she had just told me.
I then offered her a loft home but she said she had to nip to the supermarket so would get a bus, but then proceeded to walk the length of the shopping mall with me (away from the supermarket) - I assumed she was going to another shop first, but when we got to the car park it didn't seem to register with her that she wasn't going the same way as me.
AIBU to raise my concerns with DH? She's usually very sharp and 'with it', so it seemed really unusual she's coming for dinner on Sunday so should I keep an eye on her then, and then raise with DH if it continues? I don't want to cause him any unnecessary concern but I've lost a few people to dementia and I'm really worried.