A brief word about your house. Why let it go to foreclosure when it can be short saled? Short sale of a house is preferred over foreclosure. Is that a possibility for you?
It's not The Secret I'm talking about here, but human psychology. As you are a father and stepfather, you've dealt with teenagers. The more one resists, the more a person rebels in opposition of that resistance. No one likes being told "no"...right? Same with your W. Telling her that her job is no-good, she has to quit, etc. just makes her dig in her heels all much more deeper.
Given her employment history, it is pretty much a strong possibility that W will lose interest in her current job if you don't keep feeding it oxygen through your own resistence to her job. Genius? Heh...it's just pure human psychology.
In other words, don't rail against it in your convos with W nor try to stage a family intervention. Instead, do the opposite: give it zero attention. Then it will eventually die off.
I must say that you did a good job calling W out on her lies about her shaky business because it AFFECTS everyone in the house. Do what we do with the dogs during dog training: reward them for positive behaviors and ignore bad behavior. So the next time W comes to you with the "truth" on some matter, collect yourself first (ie. no blowing up) then express your appreciation to W for sharing it with you and that it took some courage for her to open up.
One final comment here. You are doing a really good job in validating W when it comes to her mother and her concerns. You're on the right track here.