Chyler Leigh with Eric Dane

When it comes to promoting Grey's Anatomy's two-hour season finale (airing Thursday at 9 pm/ET, ABC), Chyler Leigh delivers... and then some. Not two weeks after welcoming her third child into the world, Leigh took to talking up the season-ender, in which big twists surely are ahead for the likes of Izzie and perhaps George, sure, but also Lexie and her sweet romance with Mark.

Here, Leigh offers a glimpse at what's on tap this week, reflects on the romance that was not meant to be, and shares her take on two possible goodbyes.

TVGuide.com: You're such a trouper. You just had a kid, and yet here you are out promoting the season finale.
Chyler Leigh: Hey, I love what I do so... 

TVGuide.com: How was this pregnancy versus your previous ones?
Leigh: Oh, it was wonderful. It was my third baby, so I knew more about what was to be expected and listening to my body and whatnot. Yet while it was easier in a lot of ways, this was the first time where I worked throughout the entire pregnancy. And it will be the last time! But everybody was so cool on the set, bringing me stools to sit on, and bringing me water.... 

TVGuide.com: Does a part of you wish Grey's had written it into your storyline?
Leigh: You know, at first I was like, "That'd be a really great thing," but looking back, I'm glad they didn't. It would have been way too much too soon [for Lexie and Mark].

TVGuide.com: Did you enjoy the episode where they had Lexie binge-eating?
Leigh: Oh god. [Laughs] When that first came up, I was like, "OK, I get it." But I swear I gained an extra three pounds in that episode. 

TVGuide.com: Meredith had that funny line about anxious Lexie's butt getting "huge."
Leigh: Yeah, a big, fat ass. I was like, "That's sweet. Thanks, guys." 

TVGuide.com: The last time we spoke, you lamented the fact that Mer hadn't yet warmed up to her half-sister. You must be happy they have since reached a détente.
Leigh: Yeah, I'm really glad that they developed that more. I'm such a fan of the show anyway, but when she asked Lexie to be a bridesmaid, that was such a huge thing in their relationship. From Lexie's perspective, to be a part of something that big really took their relationship to the next level.

TVGuide.com: What's going on with Meredith's wedding anyway?
Leigh: They're still planning on getting married; it's just a matter of when and how. 

TVGuide.com: I must tell you that about half the mail our Mega Buzz column gets is about Lexie and Mark. Why do you think they have struck such a chord?
Leigh: I think it was just so unexpected. For me personally, when I found out about the storyline, I was like, "What? I don't get it." But you're now seeing these two characters individually grow. There's only so much of the "manwhore" story you can do, as far as Mark goes, and keep it interesting. 

TVGuide.com: Yeah, Eric Dane must have welcomed this story as well.
Leigh: It's far more interesting when you see somebody accepting change, and being proactive about it. Because the relationship between them is so new and unexpected, it raises the maturity level in both of them.

TVGuide.com: So what's next for them? What's the next big step after his meeting Papa Grey?
Leigh: Well... that comes up in the finale. I can't tell you what it is specifically, but it does definitely throw Lexie off, when Mark wants to take it to the next level. She's got all of her ducks in a row as far as what she wants for her career. Now, to have fallen into a relationship that she wasn't expecting, throws some of those plans off. It will be interesting to see what happens next season.

TVGuide.com: For all those Mark-Lexie fans, will the season end for them on a high note or a low one?
Leigh: Oh, it'll end on a high note. It is definitely good. 

TVGuide.com: Last week when Lexie was helping George with the traumas, I literally had to remind myself that those two were on the cusp of romance last fall. Were you disappointed that story got dropped?
Leigh: At first I was. I was like, "Wait a minute? What happened?" I think, though, that the reality was that George was the first person who cared about her, in any way, and gave her any sort of positive affirmation or welcome to the hospital. He was the first smiling face that she saw, and there was an infatuation factor in that — "I want to keep that around; I need that from somebody." But the depth to it wasn't as genuine as what we're seeing with Mark. 

TVGuide.com: There are rumors that the season finale features a big — perhaps tragic — development for George. Is it possible that you've had your last scene with T.R. Knight?
Leigh: Not that I know of. Not that I know of. I know nothing, and it's still too early to say; we literally just wrapped [production]. I haven't been told anything, and I'm not even sure T.R. knows, or even what's going on with [regards to] Katie [Heigl] and all that stuff, I don't know if anybody knows what's going to happen. 

TVGuide.com: So, as far as you know, you expect to see the same ol' gang on the set next season?
Leigh: As far as I know!