It's critical to define terms correctly in these types of situations.

Per Wikipedia, the Source of All Knowledge:

In the United States, the definition of sexual assault varies widely between the individual states. The Rape, Abuse & Incest National Network defines sexual assault as "unwanted sexual contact that stops short of rape or attempted rape. This includes sexual touching and fondling."[3]

The National Center for Victims of Crime states:[4]

“Sexual assault takes many forms including attacks such as rape or attempted rape, as well as any unwanted sexual contact or threats. Usually a sexual assault occurs when someone touches any part of another person's body in a sexual way, even through clothes, without that person's consent.”

Neither of these definitions apply to this situation.

Consent:

"In common speech, consent occurs when one person voluntarily agrees to the proposal or desires of another.[1] The concept of consent has been operationalized in several major contexts, including in law, medicine and sexual relationships. Types of consent include implied consent, expressed consent, informed consent and unanimous consent. Consent as understood in legal contexts may differ from the everyday meaning. For example, a person with a mental disorder, one with a low mental age or one under the legal age of sexual consent may willingly engage in a sexual act, but that consent is not valid in a legal context."

In this case, based on what she has said, this would probably be interpreted by the guy as consent. The last part of that definition addresses someone with a mental disorder; and in her case if she was manic it wouldn't have been defined as consent on her part. That being said, unless he had full knowledge of her disorder and state of mind after being high and having seventeen shots (both of them hammered), there's no way for him to bear "fault" for what happened.

IMHO, the guy is a hoser - for lack of a better term. If he was willing to fu.ck his girlfriend's friend/neighbor, then the gf should hold him fully responsible. There's culpability on both sides, and since he is still living there/in the relationship, it's likely the pair have labeled their neighbor as the offender and made up between themselves.

Rough situation, all around. There are things about which I wish I could turn back the clock, but that's simply not possible. The only hope is to look toward future possibilities.

I hope you're able to heal the relationship. Sorry you're in so much pain.