Maggie suffers heartbreak in "Grey's Anatomy" Season 13 Episode 21. In this episode titled "Don't Stop Me Now," she finds out about her sister Meredith and Nathan's romance.
Maggie is the only person keeping Meredith from getting into a romantic relationship with Nathan. She knows that her sister likes him so much, so she is willing to sacrifice her own feelings for her sister's happiness. However, the traumatic experience they shared on the plane in the past episode could prompt Meredith to break her reserve in "Grey's Anatomy" Season 13 Episode 21.
A preview for "Don't Stop Me Now" shows Meredith and Nathan enter a room full of reporters, cameras, and their hospital colleagues. It seems the doctors are being hailed for the heroic act they did on the plane when they saved the lives of the injured passengers. Amid the cameras flashing, Nathan subtly shows his affection for Meredith by rubbing her back. They also share a meaningful look, which Maggie all saw.
The look on Maggie's face suggests that she finally learns that Nathan and Meredith are seeing each other behind her back. Will this realization in "Grey's Anatomy" Season 13 Episode 21 break the sister's bond? Kelly McCreary, who plays Maggie, said otherwise.
McCreary said that it would absolutely hurt Maggie when she finds out about Meredith and Nathan's romance. However, she hinted that the sisters' relationship remains intact despite this. "But [on the other hand, Meredith and Maggie have] gone through something so extreme together, and I think the whole Nathan question has been completely irrelevant this whole time," McCreary told TV Line.
Meanwhile, "Grey's Anatomy" Season 13 Episode 21 basically tackles relationships. According to the synopsis from Korea Portal, in "Don't Stop Me Now" Eliza continues to pursue Arizona. Likewise, April and Bailey step in to help fix things between Catherine and Richard.
"Grey's Anatomy" Season 13 Episode 21 airs on April 27. "Don't Stop Me Now" was initially scheduled for release on April 20.