Need advice

Hello, I am wanting to adopt my step daughter. My husband and I have been married for almost 5 yrs and he has had full custody of his daughter for the last 2 yrs. We also have 2 daughters together. Bio mom kept denying visitation and we had been to court many times just because bio mom made the scheduled visitations so hard to have. My husband had to show up on her door step with court paperwork and the police just to get his visitation. The last visitation he had bio mom just never came to pick her up (bio mom lives in Oklahoma and we live in California) when she was supposed to go back to school so we went to court to request temp custody to put her in school while everything was getting sorted out. While we were in the process of getting temp custody we discovered that bio mom had neglected to take SD to school for almost a month because she didn't feel like making the 5 min drive. Because of those things the judge decided to change custody and award bio mom visitation. Once she found out she was going to loose child support she decided she was going to give up rights then changed her mind when she realized I would adopt. But has made it very clear she doesn't want anything to do with her daughter. It has been almost 2 years since SD has seen or talked to bio mom and even though she spent the first 5 years of her life living with her, she doesn't recognize her as her mom. She will refer to bio mom with her first name and has called me mom since she was 2. Since it has been so long we asked for permission to adopt again and she still refused to give permission but refuses to have anything to do with SD. What do we need to do to start the adoption process using 'willful failure'? Is it expensive to get a lawyer for step parent adoptions? We would like to do it without one if possible. With how much money we have put into lawyers and court fees in the past we are trying to figure out if we need to start saving up for the process or just jump in. The only thing we are concerned about if bio mom is OBSESSED with this parental alienation story she has cooked up. She tells people we stole SD and wont let her see or talk to her and wont even tell her where she is. We obviously have proof against her story but know it is going to make the process harder. Every time we have had SD call her or texted her asking to call SD she freaks out on us for contacting her and then when we don't contact her we are keeping her from SD. Is the process easy to do without a lawyer? And since we have the proof against her alienation story, would the story make the process harder? Sorry so long, there is just a very long history behind this adoption. Thanks in advance for any advice or help!