Rape is defined as sex without consent, where the (supposed) rapist did not reasonably believe the victim had consented. In my opinion, if this girl took all her clothes off and got into the guy's bed, and they were dating, it was reasonable for him to believe that she had consented non-verbally. So personally I wouldn't consider this rape, and I doubt any court would ever convict him even if there was somehow perfect proof of everything that had happened.
That said, it's a great example of why extensive communication about sex is really important, to ensure that everyone's on the same page and nothing happens that anyone's uncomfortable with.