'Teen Mom 2 Reunion' Sneak Peek: Leah Defends Herself Against Corey's Hurtful Claims

She says she's done the very best she could as a mother.

Leah and her ex-husband Corey hit a major roadblock when he sought more custody of their twin daughters on this season's "Teen Mom 2." And on tonight's "Teen Mom 2 Reunion, Part 1," Leah opens up about the heartbreaking ordeal -- and why she was deemed an "incompetent mother" in court.

"[Ali] had missed a little bit of therapy and school," the teary mother of three explains to host Dr. Drew in the sneak peek, below. "And the reason was because, if my baby comes to me and she's like, 'Mommy, you know I'm hurting,' I'm not supposed to force her, because it can overexert her."

Leah and Corey had finally let the dust settle and met face-to-face on last week's season finale, during which they expressed their frustrations with one another and explained why they each believe they deserve more time with their daughters. But the conversation -- and Corey's hurtful accusations about Leah's parenting skills -- obviously left her wounded.

"It was hard for me," she tells Dr. Drew, "because I feel like I've done the best I could as a mom."

Watch the video to hear the entire no-holds-barred conversation, and be sure to tune in to Part 1 of the "Teen Mom 2" reunion tonight at 10/9c.