We'll always have parasite
When I got remarried, I inherited a stepdaughter. At the time, I was happy about this. Though she and my husband had been estranged for many years, I was instrumental in getting them to reconcile. I've come to regret this. She is a rageaholic, spendaholic party girl. She has three DUIs and an extravagant lifestyle that's financially draining her dad and me. Though I have no problem cutting her off, my husband can't say no to his little girl — which has us on opposing ends of a bitter battle. — Stressed-Out Stepmother
If you had the traditional kind of parasite, you could just put a lit match to its butt.
Welcome to the bottomless hole of wrongheaded empathy — the daddy-guilt version of that "bottomless cup of coffee" that (if you ask politely) the Denny's waitress will keep refilling until you finally die in the booth. Obviously, your husband means well. Unfortunately, he's engaging in what's called "pathological altruism." The primary researcher on this, Dr. Barbara Oakley, explains it as an intention to help that actually ends up doing harm (sometimes to both the do-gooder and the do-goodee).
Enabling can feel so right in the moment, Oakley explains — in part because we get something out of it: activation of the same regions of the brain that "light up" from drugs and gambling. (Say hello to the "helper's high.") Refusing to "help," on the other hand, is uncomfortable and tends to lead to ugly interactions, like screaming matches if daddy says no to putting his retirement money into retiring last season's Versace for this season's Vuitton.
Being judiciously helpful takes asking the feel-bad questions, like "What's the likely result of consistently attaching a garden hose to our bank account and washing away any consequences from Princess Partyhardy's actions?" That's a question that should be answered before she gets her fourth DUI — possibly leading to a need for somebody to pick up not only the cost of the fancy DUI lawyer but the pieces of some cute 5-year-old from along the side of the road.
You can keep telling your husband this until your teeth fall out, but because of his emotional ensnarement — along with the fear and anger that you'll try to stop him — he'll probably just fight harder to go along with her little-girl-voiced shakedowns. And although, with your emotional distance, you have a clearer eye on how your step-sponge is playing her dad, there are surely a few rationality-eating emotions bubbling up in you. There's got to be anger (because your money's getting tossed down the drunken-spendy princesshole) and some fear (that you'll end up on a street corner, begging people to drop change into your "World's Greatest Stepmom" mug).
Fear and anger make for the worst argument partners. They trigger the amygdala, a central player in the brain's threat-detection circuit. It, in turn, sounds the alarm, triggering the release of fight-or-flight hormones, and shutting down functions not needed to battle or bolt, like — oops — higher reasoning. And, more bad news: When you keep repeating a behavior, your brain cells go, "Wait — we do this all the time; let's put that on auto." And this is what has happened here — which is to say, you two could be doing permanent damage to your relationship.
Advice columnists tend to squawk like parrots, "Therapy! Therapy!" (As if that option wouldn't otherwise occur to anybody.) However, in your situation — because you two can't seem to dial down the "bitter battle" — there is an intermediary you should consider engaging: a mediator. Mediation is dispute resolution. It's issue-focused, so it's worlds faster than therapy. (The mediator won't take a month to figure out how you really felt when you were 6 and you didn't get that cookie.)
The mediator's job is to dial down the emotional temperature and get you two listening to each other — to the point that you understand each other's feelings. (This is how you come to empathize with somebody — which motivates you to act in their interest and not just in your own.) The mediator then guides you to come to a decision as a couple and can help you set up a framework for discussing emotionally charged issues so that date night doesn't devolve into hate night.
Still, it's important to recognize that every problem isn't perfectly solvable. What is essential, however, is the C-word, compromise: understanding that you ultimately win by being willing to lose a little. This means accepting you won't always get the exact outcome you want — which, in this case, would probably involve picking up a time machine at Best Buy so you can persuade your stepdaughter's mother to have a purse dog instead of a child.