Complex, I agree with SRD - I would shelve the in-laws for now. It isn't your place to tell them - but you can tell your W that you won't lie to them.
I would let this go for now - and as SRD said focus on yourself. You are maybe hoping that family may rally around and the pressure will help your W turn back. It won't - and it then becomes another thing to overcome if you do ultimately reconcile...
Be patient, the truth will come out in time with her family...and then you'll probably be glad that you weren't the one who told them.
T 13 M 7 Me 48 H 46 SS 15 BD 7.14 PA D final 5.16 (H filed)
We receive & we lose, and must try to achieve gratitude & embrace with whole hearts whatever of life that remains after the losses - Dubus