https://www.hollywoodreporter.com/live-feed/greys-anatomy-favorite-chyler-leigh-to-return

The news that Leigh will reprise her role as Meredith Grey's half-sister Lexie in next week's episode was revealed in a promo (https://www.youtube.com/watch?v=8KW78A1NIZk) after Thursday's episode.

Chyler Leigh's Grey's Anatomy reunion had to be filmed via green screen (https://www.hollywoodreporter.com/live-feed/greys-anatomy-inside-those-surprising-returns)

Leigh was filming Supergirl in Vancouver, and returning to Los Angeles to film Grey's Anatomy would've required her to be quarantined. So she filmed last night's scene via green screen.

Chyler Leigh's Grey's Anatomy reunion had to be filmed via green screen (https://www.hollywoodreporter.com/live-feed/greys-anatomy-inside-those-surprising-returns)

Leigh was filming Supergirl in Vancouver, and returning to Los Angeles to film Grey's Anatomy would've required her to be quarantined. So she filmed last night's scene via green screen.