Well, I finally spoke up for myself today. I was in Rite Aid picking up a prescription and I went in the store. I usually go through the drive-thru but there were four cars lined up so I just went in.
As soon as I entered the store the florescent lights started doing their thing and I was instantly dizzy. I got a shopping cart so I'd have something to hold onto.
I got back to the pharmacy and parked my buggy off to the side (within my reach) and stood at the pickup counter. There was a woman and her teenaged daughter there, too. Their rx was ready before mine so I went to move over so they could get to the counter to check out. I didn't have my cart to hold onto and I sort of swayed back and forth and thought I was going to fall but I didn't. The woman looked at her daughter and sort of smirked and did the hand signal for too much to drink (drinking from an invisible cup).

The daughter sort of half-smiled but didn't say anything. I saw it all. I started not to say anything but then thought that I needed to set her straight.
I looked right at her and said "Excuse me but I couldn't help but see you signal to your daughter that you thought I'd been drinking. I haven't. I have MS....Multiple Sclerosis....and it causes me to lose my balance quite often. You can google it and learn quite a bit about it online." That's all I said. I wasn't mean about it but I did let her know that her actions did not go unnoticed.
She was a little flustered - probably more than she let on - and said "Oh, I have a friend with MS and I know how devastating it can be." No apology, nothing else. I just smiled and nodded and didn't say anything. I think I got my point across. Her daughter looked mortified and went to sit in the waiting area all the way at the other end of the counter!