I noticed that during this year's BronyCon too, as like the last one. The thing is, I always got this sort of gut feeling that Andrea isn't really comfortable with all the attention and physical contacts she's getting, it's just something about the way she reacts to fanboying/fangirling and offers of physical contact that seemed really familiar to me, since I do have a handful of friends who virtually avoid such things like the plague.
Hence, I never asked her for any form physical contact (I never asked for one from any VIPs to begin with), which is why I was genuinely surprised last year when she offered me a handshake last year. She did not this year, but I went with the traditional Chinese fist in palm gesture.
In conclusion, please treat VIPs with respect, as you would with any other human beings. You would be quite surprised how many VIPs would really appreciate being treated like a normal person. Also, if the VIP in question prefers not to have physical contact, there are plenty of other ways to show appreciation, without the involvement of physical contact.