This is almost word for word the same scenario but written from the DIL's perspective as one that was deleted a couple of weeks ago 'AIBU ABOUT THIS RUDE TEXT' or something similar. Same names, everything, but was deleted for being a troll.
AIBU to text my exes mum? http://www.mumsnet.com/Talk/amiibeingunreasonable/4569941-to-text-my-exes-mum