Well, it is truly up to you.
I would say that having a chat on the phone once a week is okay.
More than that?
She would take too much space in your mind and keep you focused on her.
Remember: what you want right now is to create space, not to have your mind cluttered with past memories.
Memories are fine.
There is nothing wrong with them but when you break up, it’s time to better focus on your future.
So, bring in elements which move you forward rather than hold you back.