The woman who claimed Chris Brown and his crew hit her and tossed her out of a Las Vegas party ... has now filed a lawsuit against him.
Liziane Gutierrez filed docs in Clark County, NV ... laying out the details of the story TMZ broke: She says she went to Chris' room at the Palms Hotel and Casino, and then someone -- Chris or someone in his crew -- hit her in the "face and/or arm and/or hands."
In the suit, she also says someone in the room took her cell phone.
Gutierrez is suing for battery, theft and also defamation -- over that video Chris posted calling her "too ugly" to be in his party.
As we've reported ... Vegas police cleared Chris of any criminal wrongdoing for lack of evidence.