We've already told you Bella was put off by Scott's partying the first night they were in Cannes ... but it was more than that. We're told she left at some point to attend an event, and she says while she was there, photos surfaced of Scott in their villa with another chick.

Bella says Scott pursued her in L.A. and led her to believe he seriously wanted to date her. Now she believes he used her ... never intended to pursue a relationship but wanted to arrive with a 19-year-old actress ... and all for show.

Bella finally feels what a lot of people have said ... a 34-year-old man took advantage of a 19-year old girl.