Well, I can weigh in on a personal level. In addition to my son, my brother was severely disabled, including but certainly not limited to brain-damage and autism both.
First of all: there's no excuse for this person who murdered her own child. Simple as that. Murdering a child, or your child, is inexcusable.
Second: It's a wall of text, yeah, sorry.
There's also not really a way to easily describe the mental strain of raising a child with severe autism, or with any serious mental disability for that matter. I don't know if my own son will ever make a real friend. He's afraid of other kids his own age, because they are unpredictable. I don't know if he'll ever be able to connect with another person on the level of a peer at all. He might feel lonely all the time, and not be able to tell me. He might not even be able to understand why he feels that way, ever. He might never graduate from any sort of education save for the kind that... well, doesn't have any real-world practical value, to put it bluntly. Children with autism are often impacted cognitively, but I've never met one that didn't know enough to know he was different. They understand there's something wrong, but sometimes can't know what.
There are tests, and grades, and official spectrums, but you don't really know what he's feeling or what he's capable of the same way you can with another child, not when he can't communicate. This, right now, could be my life forever. This could be HIS life forever. He could be a 2 year old equivalent for his entire life, because in the end no matter how much therapy you apply or how much special help he gets, there will be limits. There might not be any happy ending for you, or for your spouse, or worst of all for your child, and then you die, and then your child will be institutionalized who knows where because there's noone left to take care of them, if they haven't died from some other complication by then.
And through all of this, you watch your friends and family with their own children. Their children do things like graduate kindergarten, whereas yours doesn't meet the requirements for enrollment. TV shows all these happy children in commercials, and shows, and they are all so normal. They can all talk to their parents, and it's taken for granted, like this is what everyone's life is like. For a while you hope that the therapy will help, and the special education will just let them start their childhood later, or enter an equivalent program in a few years. But then, really you know it won't. All of society is geared toward helping everyone but your child live a life. Your friends with their normal kids find reasons not to spend time with you and yours. You can't even pursue a career or hobby to help with the stress, in some cases.
And how are you supposed to feel about this? Do you feel guilty? Rationally resigned? Are you being selfish? How do you know it isn't something you did? They don't know what causes autism, not really. They've had theories for decades. Could you have prevented it? Is it your fault? Did you do this? Would he be telling you about his day at the park right now instead of crying if you had been better, or more attentive? Nobody can conclusively tell you no. Or even yes.
Everything single thing in the world becomes a reminder of how alone you really are, and how your child will never really be happy the way they could have been. The world has everything for them, but they can't touch it. There really isn't a word to describe the kind of mental horror that this life eventually entails. I've seen the places where they keep the kids that they think don't have a chance of thriving. My brother died there. They are bright, and cheery, and safe, and utterly hopeless.
So I can easily empathize, but I could never, ever condone. My son can't tell me if he had fun at the park today, but I know he loves his blue striped blanket best, and big dinosaurs, and his favorite game on his tablet is Cat in the Hat. His favorite foods are grilled cheese and pizza. He doesn't like TV as much as he likes books and video games, even though he can't read. He likes cats, doesn't like dogs. His favorite playground thing is the biggest slide there. If I asked another parent to tell me about their kid, they'd give exactly the same kind of report. So in the end, I DO have a son, and he does matter, to me and to himself, and I'll be fucked if I'm not going to provide him the best opportunities and joys in his life as I can as his parent, even if it's different. I didn't make a child contingent on the idea that he graduates, or achieves certain things. When I held him for the first time in the hospital i decided to love him based on who he is, not what I wanted him to be one day. Whatever his happiness is, I intend to help him find it. Even if it's that same damn blanket until he's 20.