Teen doesn't want anything to do with birthparent but the parent has legal visitation...?

To start, my step-daughter who will soon be 16 has been living with my husband and I and her three younger siblings since her 13th birthday and we have always been active and proactive in her life before then. Before the age of 13, she lived with my husbands mother and did so since the age of 9mo's legally (But was before that even) due to the fact that my husbands job required travel and the baby was not thriving with her mother and she had 'accidents' like falling down the stairs in the house etc and the baby being too thin and not growing as expected per docs. I could explain further WHY all of this happened but it would be a novel and I'm asking you to be understanding and ume nice things? What I can say is that her father has always been a father figure to her (for the most part...when her father and I married she always spent weekends with us and we helped provide for her and she had/has an excellent relationship with us and her siblings, I wanted her to be with us full time but...I'll just leave it at that, another long story.) and her mother visited her infrequently and disappeared all together when she turned 5 (that's when hubby and I met) with the acception that on occasion a birthday card would show in the mail and a few phone calls that lasted no more than 2-3 minutes. I always kept in general touch with her birthmother, I kept her updated and sent pictures when I had them to send and encouraged and even reunited them as mother/daughter in the past...then birthmom would fall off the earth again after about a month. I didn't understand why her mother was like this until she came to live with us permanently and saw how her mother behaved towards those caring for her daughter. (((ALSO, her birthmother has a younger child who lives with another family in another state and the child has been adopted by those raising her because she was also neglected and they hardly heard from the birthmother either...same story.))) A year after we got custody of my step-daughter her birthmother sent a lawyer banging on our door with custody papers. She won some visitation on holidays and most of the summer. My step-daughter does not want anything to do with her mother and as she gets older, more independent with social life, school activities, etc. She feels burdened and pulled away by having to visit her. Their communication is HORRIBLE, they will text each other in the same room because they don't know how to talk to each other, and she sits in the house alone with nobody there for most of the summer visitation (which really defeats the purpose of 'visitation') The mother has told my husband that she will not give him a dime and has no intention to unless the court tells her to even after he's told her she needs to be a "PARENT" which means doing EVERYTHING for her child not just spending time with her when she has her visitation and basically "Play House" with her. She wants everything BUT the responsibility part of being a mother. What would be the legal reprocussions of not forcing my daughter to obide by the visitation order seeing as she is a 16yo young lady, teenager, with an opinion and feelings of her own and wants to live her life 'birthmother free' as she says. We would never make her stay away if she WANTED to visit but, she wants to visit when she feels ready to work on their relationship. So far she has visited for Thanksgiving, Christmas, Spring Break, Summer vacation, Second Thanksgiving a weekend visit (because she was in a nearby state that it was close enough ((4 hour drive)) that she could do so) and Christmas yet again. <- her birthmother was living with her dad and step-mother at the time nearby and we were asked by the birthmothers father to come get our daughter because he decided to kick her (the birthmother) out and send her back to the state she was living in...and her relationship with her mother has gone straight to hell since these visits and only gets worse (she talked to her daughter about her and her current husbands drug doing experiences and allowed the child to do inappropriate things with a boy in her presence) . What are the legal reprocussions if we didn't force her to obide by the papers