My girlfriend has kinda the same problem. The odd thing is its the flip of your situation, because she feels she is too dependant on me and worries about out all the time (even to the point of breaking up to make sure she can handle things on her own before continuing the relationship).

I think the advice of keeping calls short and sweet sometimes helps alot. I know I love getting calls just to say she loves me, and I know she loves it when I do the same. It will brighten her day because you wont have said or done anything in that time that she can analyze as anything more than you loving her enough to think to call her randomly