Leah Messer responded to criticism of her parenting on Thursday's episode of "Teen Mom 2."

The 23-year-old reality star discussed ex-husband Corey Simms' accusations on the MTV program's Season 6 premiere. Simms was seeking full custody of the couple's twin daughters, Ali and Aleeah, on the grounds Messer was an "unfit mother."

"Like I told you from day one, what I was doing was not a personal attack towards you," Simms told his ex. "It might have seemed like that, but what I was seeing I just didn't agree with," he said of Messer repeatedly dropping the girls off late for school.

"I can't say that I don't have hard feelings, because I do," Calvert said. "Being called an incompetent mother and this and that was really hurtful."

Messer and Simms came to fame on the second season of "16 and Pregnant," and welcomed their twins in December 2009. The former couple agreed to shared custody in December 2014, and Messer is also mother to daughter Adalynn with current husband Jeremy Calvert.

The sixth season of "Teen Mom 2" will see Messer and Calvert struggle in their marriage, and also follow Jenelle Evans, Kailyn Lowry and Chelsea Houska. Messer reportedly entered a 30-day rehab program for "depression and stress" in May.