1) She's much less likely to drag you to a chick flick, but way more likely to drag you to a Harry Potter flick.
2) She gets your joke about how many Pakleds it takes to screw in a light bulb.
The answer is two... one to replicate the bulb, the other to kidnap Geordi.
3) She finds the stories about the exploits of your D&D character fascinating.
4) Her response to you bragging about how you detailed your Millennium Falcon model with the blast marks in the right position: "Coooool."
5) The day after you sit through a ten hour Dr. Who marathon with your friends, she asks you if you want to watch the Dr. Who episodes she has on her DVR without even thinking you might refuse. (You wouldn't.)
6) She understands completely how cool the Midnight Harry Potter release was.
7) She has no problem meeting you over coffee just to discuss the latest episode of Heroes.
8) She thinks your facination with Superheroines and Orion Slave Girls is funny, not creepy.
9) You drop a Princess Bride reference in your conversation, and she not only gets it, but comes up with a more obscure one.
10) She's just as likely to have an attic full of action figures as you are.
11) She's not surprised that you have a Superhero/Jedi/Star Trek costume... she's just impressed that you made them yourself.
12) You don't have to explain to her who Dr. Franknfurter, Gort, Fezzig, or Neil Gaiman are.
13) She giggles when you call non-fanfolk "Mundanes" or "Muggles".
14) She insists you need to see just as many movies as you insist she needs to see.