The actress will come back to wrap up her story line in Season 2, and it is said that the show is willing to bring her back at some point. It isn't known if the actress decided to leave the show on her own, or if it was a creative choice made by series creator Jenji Kohan (Weeds).
Laura Prepon played Alex, the drug runner and on-and-off love interest to Taylor Schilling's Piper, who was also responsible for Piper ending up behind bars in the first place. The show has already set a precedent for inmates coming and going, when Danielle Brooks' Taystee was released, only to return later in Season 1.
We reported in June that Netflix picked up Season 2 of the series, weeks before it had even debuted on the streaming service. Production is already under way on the new season, although Netflix hasn't announced when it will debut. Danielle Brooks, Taryn Manning (Pensatuckey), Uzo Aduba (Crazy Eyes) and Kate Mulgrew (Red Reznikov) were recently promoted to series regulars, while Lorraine Toussaint was added as a recurring character.