how do you tell an elderly woman (that you live with) that she needs to move around more, bathe everyday, and brush her gums (don't have teeth) without being / seeming rude
Well, sorry that I find the teeth part a bit funny.
But, I think the best you could do was say: "It has come to me that you don't walk much or bathe much or brush your gums much. You should do it more often, do you need help doing it?"