Girlfriend is uneducated about sex, looking for advice

Okay so my girlfriend is interested in talking about sex and it clearly sparks an interest for her. She is 15 and doesn't masturbate and says its because she doesn't know how.She is shy so lets me do most of the talking and it's hard for her to contribute to the conversations because she doesn't know alot about it but she tries to bring it up hoping ill talk about it. The problem with me doing most of the talking is that she is very uneducated about sex so it ends up that she cant contribute to the conversation and the conversation ends up dieing when she doesn't want it too. When i say uneducated i mean that she doesn't know basic things like what a guy being hard means or what it is. She is completely oblivious about sex and I think this is because she has a lack of friends and isolates herself alone so she never really discussed these kind of things. I'm the only person she really talks to about sex and she trusts me. I guess i'm just wondering what your opinion on this matter is and how i can maybe make things easier for her when we talk or how i could possibly expand and educate her without making it clear and direct. Shes interested in talking about it but how can she talk about something she knows nothing about is what im trying to get at. I'm looking for advice.
ill make the scenario more clear and say all of our discussions on the subject are on the phone.
Thanks.

 

If she's too shy to talk about it, but wants to know more there are good websites that'll give her a lot of information about female sexuality. http://www.the-clitoris.com/ is a good one.

 

Don't overtalk about it, just when it comes up and it feels natural ask her if she wants you to show her. Then teach with your body not your words. She never took sex ed class really?

 

buy her a sex ed book. that way she can read it on her own and be able to talk to you about it.

 

ive heard good thigns about vaginapagina.com and scarleteen.com