Robyn Lively is one supportive big sister!

The 44-year-old Teen Witch star gushed about her sister Blake Lively's one-year-old daughter, James, at the iHeart80’s Party in California on Saturday, Feb. 20. “She’s just the cutest ever,” Robyn told People of her little niece. “I’m so in love with her.”

Robyn even spilled James' most recent milestones! “[She’s] walking and talking and being adorable!" she revealed. "She’s the best."

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Blake, 28, and her husband, Ryan Reynolds, 39 — who married in September 2012 — welcomed daughter James, their first child, in December 2014.