For years, Leah Messer has had hope, grace and faith—both the title of her 2020 memoir crafted using her daughters' middle names and an intense trust that everything would turn out all right. 

And now the Teen Mom star has the proof that she wasn't wrong to feel confident in her beliefs. Nearly 10 years after now-13-year-old daughter Aliannah was diagnosed with a rare and incurable form of muscular dystrophy, "Not only has she gotten stronger physically," Leah, also mom to Ali's twin sister Aleeah and 10-year-old Adalynn, told E! News in an exclusive interview, "she's also gotten stronger mentally."

The 31-year-old credits Ali's commitment to equine therapy for improvements like the news they received last year that her strength had improved and her weight and growth charts looked better than ever. 

Horseback riding along with her sisters has "given her purpose," said Leah, who coparents Ali and Aleeah with ex-husband Corey Simms and Addie with former spouse Jeremy Calvert. "And I love being a part of it with her."

Galloping into a new adventure, a recent episode of Teen Mom: The Next Chapter showed Ali approach her mom with the idea of cowriting a book about her experience with muscular dystrophy. 

"We are excited," Leah said of the project. Having the chance to share the tougher parts of her past in her book, detailing everything from sexual abuse to suicidal thoughts, "was a cathartic experience for me," Leah continued. "It allowed me to identify and really take power of so much of my life and not be ashamed of so many things. I think that Ali is going to experience the same thing. And I think she's going to bring a sense of understanding to so many other kids that maybe don't understand muscular dystrophy or that we're not all made the same and that's okay."

While so much of the eighth grader's story remains unwritten, Leah predicts a happy ending. 

"I'm always gonna remain hopeful," she said of doing her best to veer away from some of the worst-case predictions she heard when Ali was little. "Muscular dystrophy, it is a degenerative progressive disease. So we don't know what the future really looks like. But I know that we're going to enjoy every single moment now and continue to make memories and make the best of it. I think that she will continue to defy the odds."

Leah, meanwhile, is looking to surpass a few expectations herself. 

Nearly a year after ending her engagement to army officer Jaylan Mobley, she's single and ready to...network. Asked about the possibility of dating, she joked, "I don't want any distractions right now. I'm just trying to make money, okay? And raise my daughters."

She's both particularly proud of of the work she's done with her three girls ("I'm looking at a complete, better version of myself," she marveled. "And seeing everything that they love and enjoy doing, and being able to support them in their lives and be a part of it is magical") and optimistic about her own future. 

"I needed that breakup," Leah confessed of splitting with Jaylan. "I've learned a lot from my last breakup and, moving forward, I do feel like my life is just beginning."

 Teen Mom: The Next Chapter airs new episodes Wednesdays at 8 p.m. on MTV.