a) stay where i am and think "wow, it's cool that she can go out in public and not get mobbed."
b) adopt a snobbish attitude: "yeah, i'm always at the best parties and most exclusive clubs."
c) point her out to everybody sitting near me "look! look! it's donna lynch!"
d) go up to her and say something stupid like "wow, water to the dead rocks my world. i just wanted to tell you that you're a fabulous musician."
c) completely ambush her like some sophomoric fanboy: jump off my bar stool, race across the room like a spider, hold my camera out in front of me and snap a photo of the two of us so that it looks like we're hanging out and then run away so that i can tell people later "oh yeah, i was hanging out with donna from Ego Likeness last night. yeah. i'm cool. see, here's a picture!"
personally, i always seize the high moral ground.