Was it rape?

Yes. She should report this to the police.

Assuming she’s being honest with you about the facts, then yes this is rape. If you’re intoxicated you cannot consent.

She needs to discuss it with the police to go over the details. We’re just guessing and we’re only hearing a second hand account (yours). The police will hear it directly from her and they will discuss it with the man.

He was her boyfriend? Was she unconscious?

It depends largely on the laws of the country or state.

If the female is too drunk to make a cognitive decision about whether to give consent even if she agrees it can still be construed as rape because the female was not sober enough to agree or disagree in having sex.

If the female is drunk but does not consent to having sex but the the person has sex with her anyway that is most definitely rape.

I do believe that having sex with our without consent when drunk should be classed as rape.

It is, but it may be hard to prove legally.

Not necessarily. To call someone drunk is like saying the weather is mild….lots of degrees. If your girlfriend believes she was raped she will take action. You really have no standing here.

What @SnipSnip said. Even with that happening, it could be yours, if you had regular relations.

What a terrible situation, but after this I would definitely break up and take up other relationships! My advice to you is not to dwell on her now, since she herself allowed such a situation, then she herself is partly to blame for this! Otherwise, her ex would not have come to her just like that, so there were some signs ?!