I’m afraid there may not be an easy solution to this problem. You chose to marry your wife knowing her situation. You picked this family. Choices have consequences.
You can try talking to your wife about parenting. Parenting classes could help. Both of you can try reading books about tough love. Even then, it may not be enough to change the family dynamic or how you feel about your stepdaughter, but it is still worth trying.
Unless you choose to leave the family, then you must find a way to tolerate your stepdaughter. Eventually, this problem will likely fix itself after she moves out. Understandably, it may be difficult to endure but consider this: you’ve already done it for over a decade. A few more years may be doable.
Consider meeting with a therapist for a deeper analysis. They might have ideas to assist.
I wish I had a better answer for you but the reality is, not all problems can be fixed. Some problems require patience, tolerance and endurance. This sounds like one of those times. Thanks for your question.
Dr. Kristina Randle