Grey's Anatomy: Ellen Pompeo, Kelly McCreary on that Riggs twist

Warning: This story contains major spoilers from the season finale of Grey’s Anatomy. Read at your own risk!

Well, that finale twist will certainly take Meredith to new — and familiar — places next season.

After sleeping with Riggs (Martin Henderson), Meredith (Ellen Pompeo) learned a surprising new fact during the Grey’s Anatomy finale: Her half-sister Maggie (Kelly McCreary) has a big-time crush on him, which Maggie revealed to a wide-eyed Mer in the final moment of the finale.

“I so pity Maggie in this moment,” McCreary tells EW. “It’s just going to be one of those moments everybody in the audience will know except for her that she’s getting set up for some heartbreak.”

The reveal comes as the hour thawed the tension between Riggs and Meredith after they slept together in the penultimate episode. While Mer initially tried to keep some emotional distance, Riggs had the unexpected reaction — at least in her eyes — of not falling head over heels for her.

But it doesn’t sound like Maggie’s crush will stop Mer from moving forward. She’ll just have to change her tactics, which could actually help remove some of her reluctance to sleep with him again. “Maggie has a crush on him and thinks she wants to pursue him,” Pompeo says. “So Riggs isn’t something anyone can know about, so it’s very safe for Meredith, because there’s no danger there of ever betraying the one great love of her life and falling in love with him.”

Should Meredith move forward, it’s safe to expect some new tension among the sisters, especially since Maggie has always been the beacon of hope among the trio. If Maggie learns the truth, “I think she’ll be devastated,” McCreary says. “I think she’ll be really, really sad. It’ll really hurt her to find out that he and Meredith got together. But it’s not like either of them knew about her, so how can she really blame them?”

“The way that she has started to like Riggs has been very gradual and very genuine,” McCreary continues. “It wasn’t like an impulsive drunken hookup like it was with DeLuca [Giacomo Gianniotti]. Her affection for Riggs is very real. What I do think is that it’s got to cause some distance to grow between her and Meredith, just because it’s hard to be around somebody that you like and know that they’re not only not into you, but more into your sister. That would be hard to be around.”

For her part, Pompeo is excited to explore a potential love triangle, something she hasn’t done since the early days of McDreamy, McSteamy, McVet, etc. “There will be some dramatic moments,” says Pompeo, noting the situation will likely weigh on Meredith. “It’ll be a secret that Meredith has to keep, which will be good stuff to play.”

Grey’s Anatomy will return this fall on ABC. In the meantime, read our postmortem with Camilla Luddington on that Jo Wilson reveal here, and our postmortem with Caterina Scorsone on Amelia and Owen’s future here. Plus: Sara Ramirez exits ahead of season 13.