Happy birthday, Nora!
I do think sometimes we can lean a little too heavily towards feeling like someone who has Messed With one of us is entirely in the wrong, and it's occasionally useful to step back a bit and try to see things from the other POV. But our support for each other, and occasional outrage on each other's behalf, is genuine; if there's a correction to be made at times, it's only in the degree of our reaction, not in the strength or validity of our support. And of course, this is a great place to just vent and blow off steam, too, and there's nothing wrong with that.
And in this particular case, my read on smonster's situation is the same as Nora's: I think roomie overstepped a line, and when called on it, she backtracked instead of admitting it.
ION, surprise MIL visit is surprising! M's mom emailed this morning to see if she could come for a visit this weekend. (She just accepted a new job, having been laid off last month, and wanted to take advantage of her last free weekend for a while to come see us.) Fortunately, (a) I adore her, and (b) she is about the least imposing guest ever, so it's not actually a problem, but it still means we're going to have to do some significant cleaning tonight.