To be honest friend I think you should be talking to her about this. If she's not comfortable talking about it then you should respect that. If she is then ask her, you should trust her. Also I think its important not to judge her either way but hey that's just my opinion.
Also I'd agree with Tivoli, the state of the hymen is far from a sure test. Many women's hymens break before having sex, and now some even have surgery to have their hymens restored. I think a doctor could probably have a good guess with a full examination but even they can't be sure.