Could you define "she won't speak with me"? Is it because she's not available (work, family, other commitments, etc) which is fair enough, or is she free to talk (as far as you know) but refuses? How long do the silent periods last and how frequent are they? Does she suffer from depression or PMT? I don't want to speak to ANYONE for a couple of days before my period and it's probably best for humanity that I don't!!

Have you told her that her silences are unacceptable? Perhaps it's her way of getting your attention or to upset your equilibrium - both of which (IMHO) require correction.

A very few days after meeting my Master He instructed me to get a new phone which must be on and with me at all times, only He has the number and this works very well in making sure there is a constant line of communication. Would this work for you?