This is the peril of having so many eggs in one basket, and I'm afraid that it has soured you on sex as well, which is a shame, but there it is.
Call her and tell her that some things (That you are not at liberty to discuss with her.) have come up for you and you won't be available for some time (Keep it very vague.)
Resist all her efforts to pry and continue the conversation. Tell her you have to get off the phone now. (Don't do it in person.)
It sounds heartless, and in a way it is; but it is also very effective.
I've been on both the receiving and dishing out end of these converstations.
Steel yourself, and don't back pedal.
A hiatus sounds like just what you need. If and when you return to the hobby, do what I do and see a large number of gals spread out over weeks, and continually refresh the pool. This is how to keep the sizzle in the routine.