This would be good advice IF the LW has actually done something to legitimately offend the DIL, which is possible. One could argue that the DIL's treatment of LW is still incredibly rude and unwarranted even if she has been pushy; an adult tells someone when they're doing something wrong or offensive, they don't get passive-aggressively rude and nasty. OR it's entirely possible that the LW has actually done nothing wrong, and that the DIL is just a beach. I can think of two female in-law relatives like that of mine right off the bat.