It won't be long before Maggie learns the truth of Meredith's relationship with Nathan, and when that happens the relationship between the sisters is going to go through an awkward phase. But something else that is sure to spoil things for Meredith is Owen's sister, whom Nathan was involved with.
All we know about Owen's sister Megan is that she disappeared when the plane she was on went missing. Chances are Megan will make an appearance when things are going well for Nathan and Meredith, thereby causing more drama between the new lovebirds.
But does Meredith really want a serious relationship with Nathan? The pair clearly has a lot of chemistry and they seem to be bonding on the emotional level as well. But the fact that Maggie is interested in the new doctor will prevent Meredith from going after Nathan. Also, it looks like Meredith will finally take a decision regarding Nathan in Thursday's episode titled Falling Slowly, as the synopsis for the episode says "Meredith and Nathan establish what's going on between them."
What has given rise to rumours of Megan's return is the synopsis for the fifth episode of the season that states that Amelia will struggle to tell Owen some important news. Because Caterina Scorsone, the actress who plays Amelia, had earlier said we won't be seeing her character pregnant, viewers are of the opinion that Megan's return will be the important news mentioned in the synopsis.
The synopsis for Season 13 episode 5 reads: "Meredith and Bailey are at odds when both of their patients need a liver transplant, Owen seeks help from the other doctors when he is charged with babysitting baby Harriet for the day, and Amelia struggles with telling Owen some important news."
Grey's Anatomy airs Thursdays on ABC.