Season 4 was something of a learning period for Caitlin, as she first worked to balance her two personalities, and was then forced to cope with not having one of them around anymore.
So I think it’s only fair that, after she figures out what’s happening with her mysterious past, Caitlin should be permanently connected to her Killer Frost side without any risk of losing her in the future.
I definitely didn’t like hearing the words “if she can get her back” coming from Danielle Panabaker, because Killer Frost’s return should be an absolute certainty at this point, even if it might take some fairly complex situations in order to bring it about.