Being spiteful is a coping skill. (hypothetically speaking, of course).

When a significant other can shoot the breeze over household details with his own family (complete with problem solving session and a thorough tour over a couple brewskies) but won't take a few hours to visit his future in-laws, his partner is left with a decision. She can swallow her guilty feelings and her frustration that she is visiting her parents alone, drive herself up a wall trying to iron out how much she is willing to sacrifice of her own values for that of her husband's, or, she can decide to buy herself an extra pair of shoes to wear for ladies' night out that accentuate her calves. She can buy that bed set or the bathroom fragrance that has more of a hint of femininity than she usually will risk. She can decide to eat on her way home rather than wait and cook at home. She can accidentally schedule for his parents to come over on a day that he planned to spruce up his lawnmower, because it constantly needs tweaking. She can have his old ratty recliner removed and order a nice rocker that swivels, complete with swiveling ottoman. She can schedule herself for an overabundance of work hours so he feels like he's living alone, simultaneously allowing for her to earn vacation time spent with girlfriends, and/or (you guessed it) family.
Whoever thought spite wasn't a coping skill was mistaken. As far as her mental health goes, it's downright survival.