That's done ALL the time on soaps. Claudia used to be Carly...It's frustrating when it happens, but it's the kind of thing you have to get used to if you watch soaps. As for not keeping her as Star, Hulu has picked up One Life To Live. Since ABC no longer owns the show, they can no longer use the characters of Starr or Todd. They kept the actors but had to give them all new characters.
Kristen Alderson, Roger Howarth and Michael Easton (Starr, Todd, McBain) are all under contract with ABC, but Prospect Park (OLTL) owns the rights to those three characters. So, it was a legal nightmare because ABC couldn't legally use those 3 characters. They kept the 3 actors, but they legally had to play new characters.