Just go in there knowing shes like everyone else. Pretend shes a friend so you're more comfortable and treat her with the same respect.
Say whatever you feel! Just base it on how much time you think she has to talk, if she seems busy don't ask her a lot of questions but if she seems to have a lot of time to talk then ask her anything.

And of course if you don't think you'd be comfortable meeting her then don't. Hell, you could just say something like "Hey Gina, I think you're great! Looking forward to your next movie." Then tell her to have a great day and then you can leave it at that.
As I'm sure you know, Gina is extremely sweet so she will (most likely) be more than happy to talk for a minute to a fan.
Good luck! And I hope to have the pleasure of meeting her myself one day too...And I have no doubt in my mind I'd be pretty nervous at first too.
