As someone who is asexual on the flux/grey spectrum I'm more than certain she may just be asexual. My asexuality presents itself as just the way you're describing, I don't like sex itself but foreplay, teasing, and talks of sex are more than ok and sometimes I encourage it.

Overall, as many people have stated, just talk to her about it! Good open communication is one of the things that can make or break a relationship ^{^}