Is she the type that needs to be told to move on? I find some kids just wallow in self pity, so to speak and will spend the whole day crying until they are told that's enough daddy will be back at X time, now go to this until he comes.

Not all kids are like this of course but sometimes they just get stuck in one frame of thinking and need to be forced to move on to something else.

It sounds like you have done a great job acknowledging how she is feeling and if she has been doing this for over a year then a new approach will be needed.

Maybe acknowledge her feelings then stop giving attention for those feelings. Perhaps she isn't really missing dad but needs some hugs. She's just learned that this is how to get them?