I think she has forgiven Emma since she asked her if she could stick around Storybrooke to locate her father. There might still be some hidden resentment even if Emma is blameless but who knows? As for forgiving Snow and David, I personally don't believe they should just be forgiven just like that. I think they should work on earning their forgiveness. They already have started in a way. Course i was personally peeved when David referred Lily as "it" when they were searching for her while Maleficent was there and he didn't seem to care after Snow corrected him about what he said. I hope when they finally showcase Lily's journey to locate her father whether it be sometime in season 5B au in another season assuming we get one that the Charmings will lend their aid to help her to redeem themselves and earn their forgiveness. Regina worked hard to earn redemption. So should the Charmings.
I wouldn't group Emma in with Snow and David, as she had no part in what happened and I don't think Mal (or, ultimately) Lily blames her for it. It's up to them whether to forgive them au not but I wouldn't.