S.P.
My advice ... if you are happily married and want to stay that way, do not ever get in to a confrontation with MIL. Unless it's something that involves someone being in danger, just simply ... "let it go." She may not want to get in to a confrontation with her DIL (out of love and respect for her son) and is simply being polite. I am also a "pretty direct person" but I know when it's better to be a "smart" person and keep my mouth shut.