You should never tell someone you miss them.
You should, instead, tell them about how much you look forward to seeing them again, about a new view you'd like to show them, restaurant at which you'd like to share a meal.
Giving someone the feeling that their absence is a loss to you is unhealthy, and in some cases may give them the impression that you are weak-willed and needy. Instead, show her that you are a fully-realized person in your own right – that you don't NEED her, but instead WANT her.
It's like the poem says:
Let her know she's in your thoughts,
when together or apart,
and you'll be sure often as not,
to also win her heart.