I would encourage people to pet the dog, but let them know she doesn't like her face/head messed with. I take my Yorkie almost everywhere I go and people always fawn over him as he is adorable. He does pretty good but when people try to reach over his head he will duck a little. I typically give little kids his back to pet while I have his head toward me and he doesn't mind at all.
I have only had my 9 year old Yorkie for 6 weeks so he is still adjusting. I can do anything to the dog, except brush his teeth. I think I have scars from that, but that is another story altogether. It took time for him to learn to trust me though. I could not hold him on his back like a baby until I had him a few weeks and now he loves it. These people you see won't see your dog enough to earn that kind of trust. I would just say "Sure, she loves attention, but not at her face." That kind of thing.
I hope it works. Mine does pretty good with most people touching his head though and I hope it gets better as he adjusts even more. He is the greatest dog I have owned and I adore him.
