I will give it your W that she does appear to own a set of brass ones. I like the response above "Gee, W, I am sorry to hear of your financial troubles and I hope things turn around for you soon".
Say no more, no less. You cannot control her reaction so let her get mad, swear, yell or do whatever she is going to do. WAS that cheat dont get help on new car payments. Your W is nice to you when she needs something, otherwise she has made it clear you are highly disposable to her. This is your chance to begin setting a precedent - this will *not* continue.
You can validate her concerns and show compassion but that is it. This is a GOLDEN opportunity for you. As Ari Gold would say.... "silence is golden, Loyd" (are you an Entourage fan?). In your case... "silence is golden, Kevin"
