Personally I would say absolutely NOTHING. I know the temptation to start up some kind of rapport is overwhelming, even if it just so you can unload your rage, but right now how good does it feel that she has chosen to take the wrong path and even though she hurt you more than anything, she is now getting bite in the ars by mother-karma.
How sweet will it be if her trainer leaves her and she is left in the complete wilderness. I know that doesn't help you in terms of not feeling pain anymore but it will certainly make things a little sweeter for you in the long run.
Don't say anything. She hasn't been through nearly enough to warrant your attention.