Sawa Pontyjska told BBC News she's all ready to go with a legal complaint against the organizers of the film festival ... claiming she was assaulted by a female security guard while attending the "Marcello Mio" premiere -- something that was caught on camera.

Footage of the face-off went viral during the event, especially after the same security guard got into an argument with Kelly Rowland earlier in the day.

The staffer in question has been busy --- also having viral incidents with K-pop star Yoona and actress Massiel Taveras ... facing backlash online for seeming to rush them off the red carpet and, at times, seemingly getting handsy with them.

According to Pontyjska, the female staffer put her in a "bear hug" while she was on top of the Palais des Festivals staircase ... saying she was brutally restrained.

She added ... "I was trying to escape from this lock. I went down, and I started to run away on the stairs because it was the way back [out]... She was trying to push me in[side], so nobody can see what she’s doing with me. Then she kicked me out through the back door."

The clip from the red carpet appears to show the security guard attempting to drag the model inside the venue ... with several other ushers intervening as Pontyjska tries to wriggle free.

In addition to alleged physical and psychological harm, the model reportedly also claimed her rep has been harmed by the incident ... and she says she's seeking 100,000 euros in damages. We haven't been able to track down the lawsuit, BTW -- but Pontyjska reportedly posted photos of the docs on her social account ... which appear to have been scrubbed.

Anyway, Pontyjska was calling on her Instagram followers to help her get "a serious lawyer" -- and it sounds like she might've found one -- 'cause some outlets say the suit's been filed.