I read the autopsy report over at The Smoking Gun. I'm not a medical expert by any means, but I don't see a thing in that report that suggests prior sexual abuse. Yes, there were abrasions and blood in the vaginal area, but there was hymen tissue from what I can read. It doesn't appear that there is enough of the hymen missing to indicate prior sexual abuse. Perhaps she didn't ever have a fully formed hymen, perhaps it was torn during the sexual penetration of a "foreign object" during the attack that killed her, or perhaps there is still another perfectly innocent explanation.
In any event, it appears that there was enough of a hymen present to rule out prior sexual intercourse - from my admittedly untrained medical eye.
I just hope that people speculating on this subject have done their homework and read the official reports and not rely on other's interpretations. Certainly don't rely on my interpretation - go read it for yourself.