QS, you have to keep them informed when she lies to them.. and show them proof...
btw what the heck is her FATHER doing? Just sitting on his ass or something?
Fathers tend to be better hardliners than mothers anyhow I think... Keep telling them the truth and keep them informed... WARN them about the risks of empathizing with her crying and whining ...
If MIL is ratting you out tell her explicitly to keep her trap shut or better yet, only tell her what you are ok with wife hearing.. and most of hwat you tell her isn't anything problematic anyhow... warning her by showing her that video is not going to ruin anything for you...