Rant about my stepsons mom😒

So my stepson is going to be 4. I was flossing his teeth the other night and his teeth like crumbled and I realized they were decaying. I confronted his mom and she was like “ oh yeah I know, I’ve been meaning to take him to the dentist” and she said she felt like a shit mom. She lives off of us and hasn’t had a job in the 4 years I’ve known her. I’ve been with my husband since my stepson was born and have been the one to potty train, wean him from the bottle. I buy him clothes and take them to her. I arrange pick ups and drop offs for him. I give him all the insurance info for him to her because we cover him for everything. We literally are there for everything he needs and more. We try to keep everything between us simply between us and not involve him in anyway. As far as he knows we are one huge happy family. But while being in her care he has had a broken arm, pulled a coffee pot off a counter and cut his face open while she showered and left him alone in the living room when he was a little over a year and he now has a scar across his face, she lost him outside and had to call emergency services to help find him because she let him go outside by himself while she stayed inside. She has picked him up after she was out drinking all night. I thought something was up but couldn’t be 100% sure until she posted pictures herself later that day from when she was at the bar In the same clothes she picked him up in and she hit a pole ( I’m pretty sure) but said it was a deer, and she stopped 3 times on the way home to sleep while he sat in the backseat, I’m furious with that one. That happened a couple months ago. Any way his teeth. I had to take him to a pediatric dental facility to find out how extensive the damage was. You guys...... he has decay on almost all of his teeth. And 14 cavities...... he has to be scheduled at a surgical center for surgery to drill all the decay out and put on veneers on all his teeth. We traveled to this facility and they squeezed us in because they were booked out 3 months and we drove over two hours to get him seen here. So after wards we got the treatment plan and it’s going to cost around $5,000. You guys ..... $5,000. So I talk to her tell her she needs to stop giving him coffee.( just found out she’s doing that) and start brushing, flossing, and doing mouthwash and all the work that needs to be done and we can get him scheduled to have everything done next month since they want it done asap. This bitch goes “ oh, I want to get a second opinion done and see if I can have it done here” and I tried to explain how severe this is and how it needs to be done at a surgical center and have him sedated because of how much needs done. Well she’s flat out refusing and I’m almost certain she’s not going to take him to get that second opinion and I’m half tempted to just keep him here until we get all of it done. And my husband is being way too nice. Like extremely nice about this whole thing. And I’m like are you kidding ? We were told he is going to have issues with his permanent teeth due to this . My husband never wants to have conflict with her and I am straight up angry. This child is severely neglected obviously showing his lack in dental care and there’s more I won’t get into. I just really needed to rant. Thank you if you stayed around this long. I really need some support here because I am a momma bear with 3 kids including my stepson and currently pregnant with another and I feel like I’m alone fighting a losing battle.