On Grey's Anatomy we learned that unlike the last piece of pizza, you can't call dibs on love. "The Don't Stop Me" episode finally addressed the romance that has been fruition between Nathan and Meredith, even though Maggie was the one that first called dibs.
Meredith had planned on talking to her sister about the budding romance, but she figured it out on her own. During a press conference about Meredith and Nathan's harrowing flight, Maggie noticed that Nathan rubbed Meredith's shoulder affectionately. Then Meredith noticed Maggie noticing and just like that the cat was out of the bag.
Maggie was displeased, to say the least, and refused to talk to Meredith about stealing her crush. But fortunately Meredith persisted and they finally talked about it. And as time heals all wounds, by the end of the episode the two sisters were backing to being friends.