While I can appreciate the honesty in the message (re: too painful to pretend), she may not.
Personally, I would have left it at: "I am not available to come this time, hope to see you soon." or something of that ilk.
As to her keeping it to herself, well, I think it's better not to say it if you do not want it repeated back to your H. Blood is thicker than water.
You can be true to your feelings without putting it out to the world exactly what they are and it might help you to feel less judged that way.
If you think a particular situation is not going to work for you...don't go. You do not have to justify why to anybody. Being busy might mean you sit on the couch and read. Just sayin'
