Some thoughts from a not-so-good female player, but one who is totally hooked:
Take her with JUST you the first few times. I've only been playing a couple of months, and while I enjoy playing with our other friends, I'm less tense when it's just me and my guy playing. It's one thing to not throw well in front of him, but a whole different thing to throw poorly in front of his friends. When I do throw poorly in front of him, I'm still comfortable and don't get too upset. When we're throwing with friends, I put a lot more pressure on myself because I don't want his friends to think I'm a horrible player.
Encourage her, but don't be too overly enthusiastic. What I mean by this is, if she makes a good throw or does something right, tell her. If she makes a really crappy throw (a ten foot drive off the tee or something), don't tell her that it was a good throw -- she'll see right through you and, most likely, will be pissed because you're placating her.
Remind her that everyone struggles when they first begin and that it just takes time and practice to learn.
Show her proper form and grips, but if she's found something that's working for her, even if it's not totally right, let her use it. Offer tips when you see that she's doing something that's not quite right, but don't do it after every single throw.
Buy her a couple of her own discs...in her favorite colors. My very first disc was a surprise gift and is a pink Valkyrie, which made me even more excited to go throw the next morning. I threw it for a couple of weeks and then decided that I wanted some more of my own, so, on a whim, I bought an Archangel. The very first day I threw the Archangel, I had my best round, which made me feel good and even more excited to play. I couldn't WAIT to hit the course again! Sure, it's light enough that I couldn't throw it in a tournament, but at this point, I'm just playing for fun….and it's a lot more enjoyable to actually throw decently. I figure that I'll work my way up to a heavier disc eventually.
I'm very lucky to have an extremely supportive boyfriend who offers hints and tips to me (but not when he knows I won't take it well) and treats me like it's as fun to play with me as it is with his friends who are good. As a result, I LOVE the sport and am totally hooked!