Don't mess with Amber Portwood! In a trailer for the season finale of Teen Mom OG, Portwood lunges at her on-again, off-again fiancé Matt Baier when she learns about his cheating scandal.

"I told him if he ever cheats on me I'll leave," she said in the sneak peek.

The trailer then cuts to a man holding Portwood as she tries to attack Baier while screaming, 'You f**king b***h!'

On last week's episode, Portwood learned that Baier had been texting another woman.

"There's fake f*****g text messages supposedly," Portwood said of messages that emerged between Baier and another woman on social media. "Talking to someone else like a year and a half ago. I told him in the car we need a break. This is too much. It just keeps making me doubt everything. I need to figure out what's going on with all this s**t."

As Breaking Celebrity News reported, Portwood called off her engagement to Baier when he failed a lie detector test about the text messages in May. Although they were "still living together" at the time, she revealed over Instagram live earlier this month that they are not together.

On the Unseen Moments special, Portwood admitted that her ex is a "huge pathological liar."

"He needs help," she said. "If he wants this relationship to work he needs to change his lying."

But not all hope is lost for the couple, as they are currently in Los Angeles together. Breaking Celebrity News exclusively reported that they are filming the upcoming season of Marriage Bootcamp: Reality Stars.

Portwood has a history of violence. The mother of Leah, 8, was charged with domestic violence in 2010 after she was caught on camera slapping and pushing ex-fiancé Gary Shirley.

On last season's reunion special, she slapped Farrah Abraham across the face when she said Baier looks like a pedophile.

Ru