Mom sometimes not recognizing dad; any tips or guidance?

My Mom (72) has had Alzheimer's since 2013. In the past two months I noticed her becoming more anxious and disoriented.

Recently this included calling me up while dad was napping and saying somebody was in the house and she wasn't comfortable with it. I would ask her about dad and she'd ask "my dad?" etc. She seems to even forget his name at this stage.

Notice that this is happening but she is able to remember me and pick up a phone and call me, which I find surprising.

These have only happened a couple of times and seem to be when she first wakes up from a nap or in the morning. Once my dad steps in it seems like she gets re-oriented and is fine.

We were speculating that maybe she's not getting enough fluid?

We are going over often and having her over for dinner often. I am even interviewing a part-time caregiver to give Mom more social stimulation.

Does anyone have any tips or guidance for this stage?