I doubt these creators/writers would have cast the role of Belle like they did if they didn’t have a definite plan for the character to play a pivotal role. They knew Emilie from her days on Lost, so I’m guessing they wrote Belle with her in mind, so they have a plan and whatever it is, it’ll be good stuff, of this I’m sure.
I wouldn’t want to see her killed off. I’d like to see Rumple having to work at it to win back her love, which will ultimately be his redemption and her salvation.