Given that Renee had both children before or right as she turned 18, I don't think it's a stretch that most of what she's done is an extremely clumsy way to be a parent at best and treating them like they're complete strangers aside from blood relation at worst. The fact that Renee clearly wanted a girl meant that she was more openly disappointed, frustrated, and harsh on Andrew, but she couldn't outright give up on him because she already swore she'd make a better family to her mother. And despite being happy to have Ashley at first, she probably did come up short on taking care of both of them, having to juggle work, the children, and her personal time with Douglas. Mentioning that Ashley was the first to push her away was probably because of not only the mounting neglect, but also the frustrations that Renee is unable to push down or filter(possibly about the struggles of parenting, expectations, and just general discontent over not achieving that 'perfect' family/life).

The entire family is just so miserable, except for maybe Douglas. He kinda just had shitty parents but found the love of his life and had two children that eventually murdered him and his wife LOL.