My mom who has not been diagnosed with dementia by her regular doctor, but who exhibits all its signs, has gotten into a habit of calling me on her iPhone and saying that she saw my call on her phone, and then say "Oh, sorry, I am having so much trouble with this phone, I am helpless." She keeps doing that, even though I call her every day, or every other day at the rarest. Also, she's been sending text messages with her photo (that is taken inadvertently when she pushes the camera icon on a text message) in the middle of the night. It wakes me up, but I don't want to set my phone to do-not-disturb, as I want to be connected to mom, in case she really needs me. When I called her to tell her what happens when she pushes the camera icon and sends a night message, she sounded perfectly aware of that. "Yes, I know that," she said, and "Sorry if I woke you up" in a slightly angrier tone. I am contemplating a move away from my kids and a grandkid, and back to the town where my parents are now, and I don't know if I'll have the patience to be a good daughter... Yet, I feel for her... She and my Dad are together, and he is more lucid, but he pretends that nothing's going on with my mom, and they reject any help from me...
Your mom is perhaps recognizing that things are not quite right and has developed this compulsion to connect with you. I agree with babalou, get her to a doctor for a work up. My mom has benefited greatly from medication.