
Bristol told People.com that Levi -- father of their 19-month-old son Tripp -- told her about his scumbaggary on the same day they announced their engagement ... but that wasn't the final straw.
Bristol claims she decided to pull the trigger on the relationship after Levi lied about a recent trip to L.A. ... when he said he was traveling for a hunting show ... and instead shot a music video mocking the Palin family.
As for Bristol's mom -- Sarah told People.com, "Bristol is strong, she is independent, and she knows what is right for her son."









