I've gotten brave in my old age so I probably would have said something to her. I'd have been nice......but I would've pointed out that I have MS, too, and asked her if she considered me "retarded" (and also let her know that term is inappropriate and insensitive). Basically put her on the spot and make her think about what she said. If it made her uncomfortable or embarrassed her in front of her friend then even better!

Chances are her boyfriend has cognitive problems that she doesn't understand (or doesn't want to take the time to learn about). For his sake I hope she takes a hike.

Let it roll off your back.....and be thankful that you aren't like her!