Would you say something to someone who invaded your personal space?

I was at Subway today and standing there watching them make my sandwich and the woman in line behind me was having her sandwich made by someone else at the same time. I was sort of in the middle of the counter thing standing right across from the guy making my sandwich. The person making her sandwich was right next to the one making mine and so she decided that she needed to stand directly across from him and snuggle up to me. We were the only two customers in the store, so it's not like it was crowded or anything. And so I kept inching down and she kept going too! She was literally touching my arm with her arm. It was the creepiest thing ever. I didn't say anything, but I kept thinking "Should I ask her to back up?". Anyway, what would you do if someone was freakishly close to you?