Women can't sexually assault women. Forced sex is sexual assault. Forced penetration with fingers or objects, or forced contact with another person's sexual organ is sexual assault. Drugs and alcohol are the reason for most sexual violence. Drugs and alcohol can inflame emotions, but they do not cause sexual violence.
Perpetrators sometimes claim drug and alcohol use as an excuse for having been violent.
For many reasons, including homophobia and heterosexism, many gay, lesbian, and bisexual victims are reluctant to admit or report sexual violence.