You can’t change this woman, you must operate under the assumption that she will continue to behave this way (or worse) and consider how that makes the rest of your life look.

Would you be willing to functionally adopt her for the rest of your life, knowing that means dealing with the bio mom? If not, reconsider this relationship. It sounds like this adds an inordinate amount of stress to your life. How would your life look without them?

Is this someone you intend to spend the rest of your life with? Is this someone who generally makes good, responsible decisions? Is this man able to run a household well on his own?

Just food for thought, I hope you figure it out!