My mom has had two strokes (we know of) starting five years ago and with Broca's aphasia as a result, but her speech has come back almost 100%. Recently, we've seen her state things repetitively and it's kind of scaring us. A few weeks ago, it was "No one comes home to take care of me." over and over and over. And it wasn't woven into conversation, it was just stating a sentence. Today for instance, she was staring at her hand for some time and then kept repeating, "How did I get so old?" I was nonchalantly recording this because I needed to show it to family members. She must have said it ten times in rapid succession. I know AD patients have repetitive phrases and questions, but she's never had a diagnosis of AD.
Vascular dementia is the usual suspect with stroke survivors; and another common feature is depression (the brain chemistry sort, as opposed to the reaction to events sort).
In any case, it's important to report any changes in behaviour, mood or physical/sensory abilities to her doctor; so I should start there.