The Kick-Ass 2 star tweeted "please pray for my mama."
Moretz responded "thanks Abbie" to Breslin.
The 16-year-old's mother, Teri Moretz, has been battling cancer, and the Carrie actress recently opened up to UK InStyle about her parent's breakup and her mother's diagnosis.
"It made me realize, along with everything that happened with my dad, that your parents aren't these godly figures," she told the magazine. "They're not chosen by the heavens. They're humans. Their bodies can fail and they can die at any moment. They make mistakes. They cry. They fight. It definitely, from a young age, put everything into perspective for me."
Moretz is also homeschooled, and her mother serves as her teacher. During a recent appearance on Chelsea Lately, Moretz told Chelsea Handler that they are both very accommodating to each other's schedules.
"She understands that I like to sleep in because I get all these hours when I'm working," Moretz said. "I get like 6 a.m. starts, so we start school around 9:30. We work will 6 p.m. but it's worth it."
Stay strong Chloë, our thoughts are with you.