grandparents right to protest adoption

I am starting the process of adopting my step daughter. She has lived with me and my husband for 2 1/2 years now and has little contact with her birth mother and maternal grandparents. Her grandparents actually make more of an effort to contact her, then her mother does. She has seen her mother twice in the last year and that is because we took her over to her grandparents and her mother visited with her there. Other than that, she makes an occasional phone call and makes all of these promises of visiting and then we won't hear from her for 5 or 6 months. She has not contributed financially at all in the 2 1/2 years we've had my step daughter. I am pretty sure she will fight us on the adoption but we are going to try to prove abandonment due to the lack of finacial contribution. Not to mention, that the reason my husband even has custody is because of CPS removing the children due to drug use and domestic violence on the mother and her boyfriends part. Since my step daughter has more contact with her grandparents, can they contest any part of this adoption? My husband let them know what our plan is and they understand our side but this is their daughters child we are talking about.