Sarah Chalke, Brittany Snow Sarah Chalke, Brittany Snow

Brittany Snow will guest-star on CBS' new romantic comedy Mad Love as Sarah Chalke's sister, the actress tells

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Mad Love follows the story of Kate (Chalke) and Ben (Jason Biggs), who find romance on top of the Empire State Building. Unfortunately, their respective best friends — serial rom-com best friend Judy Greer and Reaper's Tyler Labine — aren't too fond of one another.

"It's an interesting episode because it's really funny about how overprotective Sarah Chalke's character is towards her little sister," Snow says. "My character wants to break out and just go crazy. There's definitely a side of my character that she shows to her sister, and then there's a side that she's actually doing."

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Snow shot her guest spot a few weeks ago while also filming Harry's Law, NBC's new legal dramedy, which debuted to 11 million viewers last week.

Snow, 24, is best known for her roles on American Dreams, Guiding Light and Hairspray.