"Teen Mom 2" star Leah Messer-Calvert has big news to share about her daughter Ali.

Though a doctor told Leah that one of her twins would be confined to a wheelchair, the reality TV star now says she's doing great.

"Ali is running," she says in a new interview with In Touch. "She has so much determination. We're in awe of how she handles adversity."

Ali was diagnosed with a rare form of muscular dystrophy.

"The disorder affects her respiratory system and progresses the older she gets," the 21-year-old explains. "The bigger she gets and the more weight she gains, the harder it’ll be for her muscles to carry the weight."

But, according to Leah, "She's doing so much better than expected. This is proof that we should never give up hope."

The "Teen Mom" star has twins Ali and Aleeah with ex-husband Corey Simms. She also has baby Adalynn with new husband Jeremy Calvert.

We're glad to hear they're all keeping a positive outlook.

Check out the gallery above to see how big the twins have grown since filming the current season -- they're so cute!

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