u/pastelmango-911

I live with my boyfriend and he has joint custody of his daughter 50% of the time. She is 16 years old. She has had a best friend for about three years who has had a rough home life, the father died a couple of years ago and the mother is in prison. She’s getting raised by her 80-year-old grandfather. Something has been happening lately and I just don’t know how to handle it. My boyfriend and the 17 year-old girl have been engaging in heavy flirtatious activity. Up until recently, my 16 year-old (I will call her stepdaughter) has not picked up on this activity however, we are both highly upset now. We went to the beach last week for five days and immediately they ramped up they’re flirting. My boyfriend adjusted the rearview mirror of the SUV we were in so he could look at the girl and they locked eyes and smiled through the mirror. I confronted my boyfriend about it, and he cussed me out and called me a jealous old woman. He told me I was crazy among other things. Throughout the week, several other things happened and at one point, they were both almost blatantly flirting in front of us. Examples could be the girl getting up and walking in front of my husband and stopping right in front of him so he could look at her body. He did the same exact thing to her. On the last day at the beach, my stepdaughter came up on the beach where he and I were sitting, and the girl was with him and I stepdaughter made a comment that she had had fun at the beach and that she felt like it wasn’t long enough and didn’t wanna go home. The other girl chimed in and said a few things agreeing to that, and my husband looked at the girl up and down and said well, you know what they say with anything good. Once you get a little, it keeps you wanting more. And he smiled at her the entire time and she giggled like she thought it was the funniest thing. The girl has also told my stepdaughter that she is planning to find a sugar daddy as soon as possible. When I got my stepdaughter one on one home after the trip, she and I had about a three hour discussion and she told me some other disturbing things about the girl. She said that the girl had been kicked out of another set of parents house already, and that she had been flirting with the dad. This particular father wanted nothing to do with it so they banned the girl from their home. I even tried to talk to my boyfriend later on and let him know this information and he said oh I’m sure it was because of a jealous old wife.
There are many other things that I have noted over the past couple of months as well, which seem off. I’m starting to wonder if there could be a possible grooming situation that has been taking place right before our eyes for the past year or two. I’m really thinking of calling DCS, but I have contacted someone that I know and they said that with little proof DCS won’t do anything and it will definitely come back on me. I really do not want them to find out that I did it and so I don’t know how to go about turning this in or even if I should. I don’t know that anything has been done physically yet, but if it hasn’t, it’s on its way by the time she turns 18. I feel like action needs to be taken now to protect this girl. However, I think she also needs protection from herself.
I don’t really know what else to do at this point, but I’ve considered talking to the girls boyfriend who is 18 or I’ve considered talking to his parents, but I’m afraid that would also backfire on me and my boyfriend would find out that I did that.
I’m so upset and hurt and he is blatantly lying to my face. My stepdaughter has blocked her on social media and stopped talking to her and she is blowing her phone up because she can’t come over. I really don’t want my stepdaughter to have a confrontation with this girl because she’s a non-confrontational child. I just don’t know how to handle this. Every time I bring it up to my boyfriend, he completely blows up at me and tells me that I’m accusing him of being a child pedophile. I do think this is a tactic just to shut me down though.