I agree with
@Miss Anne Thrope with one exception: Icthink Chantel was wanted early on, until she became hard to handle, which was pretty young Her obsession with food started early when grandma babysat, all her memories from 3 on are of food. And, so did her tantrums. A young, teenage mom just might not have the knowledge to say no and discipline to listen to screaming in order to teach boundaries. So they probably started out with a poor dynamic with mom saying no, Chantel screaming, mom giving in ad nauseum, and she was finally shuffled to grandma to give mom peace. But she came back and the dynamic continued. It eventually got to the point where mom sent her away to camps and outdoor things since she couldn't teach or control her.
By the time Nat was born, mom was more settled, married, older, understood how to raise a child better, plus Nats natural behaviour isn't to screen to get her way. So they made a peaceful family that Chantel disrupted and it was clear she wasn't wanted. At home or school. But this is partly Chantels fault.
She wasn't going to be popular girl at school either but her focus on food and misogyny assured she was disliked. The only way she thought she could have friends was to screw men but of course, most girls find that creepy. Her friends were other losers like Peetz. or people who felt sorry for her, and they've dropped away. She doesn't miss human connection because she has this fake online thing going.
She wasn't wanted, I agree. But it was because she became too difficult. If she’d matured and managed to fit in and be nice and peaceful it’d be well.
The fact that her family was begging her to go to therapy and offered to pay for it shows me they see how out of control she is, and don't know what to do yet still love her. And, there is no doubt fear that she'll have no place to go but with them.
And if that ever happens, they better get therapy themselves to learn to ignore Chantel and her tantrums.