How do I deal with my daughter’s adoptive father’s cruelty to her?

Open adoption 19 years ago. The adoption mom/dad where always very open to visiting etc. In fact they even would stay at my home when in town. As my daughter got older they allowed her to come a stay at my home with my husband and I as long has her siblings were welcome to come with her. Of course they were welcome. So a very open relationship.  3 years ago my daughters adoptive mother passed from cancer. She just turned 16 when that happened. Her adoptive  father quickly moved on and several hours away. when he met a new lady and then remarried within a year. He is so selfish and unthoughtful with my daughter.  My daughter was especially close to him. Over the last few years I have become aware of a very poor and manipulative relationship she had with her adpotive mom. Her older adoptive sister told me stories and so did another member of her adoptive family. Her other mother was maybe depressed or bi-polar I really dont know. For a couple of years now I have seen her adoptive dad break her heart over and over.  He even literally left his other adopted daughter at a park with his grandson and drove off with his new wife. Drove off to his home 3 hours away and just expected her to call a friend or other family member to step in and help her. He is a fool.  When she drives 3hrs to visit him  he ignores her when his wife is around.  Her older sister will not even talk to him because of how he has treated her and her son. I know he has to love her. My daughter has a younger sister who is two yearsto younger and whoi is theonly biological daughter of her parents. She alsois has a 6 year old and another who is adopted. She wants to keep a good relationship with her siblings in spite of how her father treats her. I understand that desire but I am so disgusted with his hatefullness and coldness that I cring when she goes to visit that she will be treated poorly. This is a strange situation but does anyone have a similar experience. How can I guide her, how do I keep from shaking him? She picked a collage in the town where my husband and I live, has a room in oir home and we never skip a day without talking. She even stays here a few days every week instead of her dorm. She adores my husband and he adores her. I met him a month after she was born so they have known eachother her whole life. I worry she will trust noone because of the abandonment she must feel. First being adopted, then her adoptive mom dying and her adoptive dad moving while she was still in high school. I encouraged counseling and she went a few times but said she doesnt think she needs it.