Actually, no that's not necessarily true. Every situation is different, and some women are not visibly bruised/injured after a rape. That's one reason why it's so hard to prove when it happens between people who know each other. It all depends on a number of things, how much she physically resists, how rough the penetration actually is, how much lubrication is put out by her body, etc (sorry to be a little TMI but that's the facts). As the doctor said, a woman who's sexually active may not show as much evidence of "forced entry" after a rape. If her body is used to that, she is more stretched and not as easy to injure. Plus, since her body is accustomed to sexual activity, it's likely to be more responsive to sexual touching, even if it's unwanted. A woman's body can respond to a rapist's actions, she can even have an orgasm, even though sex is not wanted, the body can still put out lubrication and be receptive to the sex. It's also possible she may have stopped resisting him early on simply put of fear, which might have lessened her injury. A rape exam can definitively determine if sexual activity has taken place, but it can not always definitively prove whether or not the sex was consensual.
Excellent response. Thank you. So many people don't understand this. I've been in many rape support groups and even women who were raped are often confused if there is no proof of forced sex. So many including myself blame themselves.