What would you like to do with her @cranky_granny? I truly believe we teach people how to treat us by the way we interact with them. Can you be honest and say you don't feel up to talking about it today, and then maybe plan something you could both do together that would benefit both of you? You say that she is using you as a distraction from her problems? If that's the case, why not suggest both of you taking some time off from your problems and going to the movies/shops/dinner …. just taking some time out to get away from it all and enjoy being friends.
Personally, when I want someone to back off I'll resort to giving them "the look" and holding up my fingers in the sign of a cross and saying "back off" (a quiet growl if I know them well). Direct communication works for me :wink: