Thanks for the suggestion. Been there, did that. Over the last decade-ish she’s had a series of TIA “mini-strokes” and those have left small holes the MRI can readily see.
Her overall age and health is such that’s she’s just starting that final set of increasingly severe wobbles that ends in eventual collapse. We are actively managing what we can that she’ll let us. At least she’s in a happy place mentally & emotionally. I think one of the TIAs gutted her “worry center” and that has been a very good bit of luck for everyone involved.