One phrase that Aaron Boster uses regularly in his You Tube videos about MS is that “Sometimes Mother Nature can be too generous” in that we can have additional diseases beyond “just” MS. That is that having MS doesn’t make us immune to other health issues. They can check her MRIs for black holes and atrophy that could be related to MS but consider, too, that she may have a compounding medical issue leading to this. My mom had Parkinson’s and while these symptoms don’t sound like that she gradually lost her interest in anything beyond her sight and then her reach and had a hard time understanding many concepts and conversation. It is hard to “lose someone” while they are physically right here with you. I’d encourage you to look at all possibilities but know that MS can cause significant cognitive decline as well. Hope you can find something that helps.