How do I get my sister to stop abandoning her son? I hate her.

SO.

I totally just needed to get this off my chest, even though it's been going on since Max's birth.
My nephew is about 15 months now. He's the most adorable, crazy, cheeky, chunky, chucky monkey you will ever meet. Photo's are on my profile =]

My sister, Nicole, is turning 26 next month. She has a boyfriend, Shaun, who is a child predator. Got caught talking to what he though was a 14 year old girl online, telling her how to masturbate, saying he'll fly to where she lived to have sex with her. He was arrested at the airport. That "girl" was an undercover cop. He's on probation at the moment. No internet, no alc/drugs, can not be alone with children. And right there, you know something's wrong with my sister if she's still with this sick c*nt. He looks like David Bain, no joke.

I can't really remember when it exactly started happening, but after Max was born, and has returned to work, she started not coming home after work. It was one night, she was home the next day. Then it became a whole day of not being here. Now, it's up to a WEEK at a time.

She won't answer her phone, even when her boss calls. She'll never txt to say, "hey I'm not coming home for a week." We never know where she is. My mum would call Shaun, who is 34, lives with his parents, and he'll say, "I don't owe you anything."
My mum, after we found out about him, said he was no longer welcome anywhere near our house, or Max. So he's only seen Max maybe five times since he was born, in the first few months when my sister wasn't at work yet. They work together.

Of course, mum and I would have to look after Max, mostly she has to lean on me because of her health, she can't keep up with Max. I would often take days off course to look after baby, so mum could do groceries or whatever, have a break. Sometimes Nicole would leave with his car seat, or pram, so mum couldn't take him out with her. Even my 14 year old brother kisses Max when he comes home from school, and says, "I'll play with you after my shower, ok?"

Every time she came home, mum would ask, "do you even remember this boy? He's your son. Look at him."
And it would take an agonising hour or so for her to even look at Max, crying on the floor. She doesn't speak a single word when asked where she's been, why she runs away, bla bla bla. Nothing. Mum's now reading her txts, looking in her bags, I've hacked into her Facebook, her boss keeps in contact with mum. Nicole will spend her entire pay on motels, smokes, food, gas. No food or nappies for baby, oh no. No board for mum.

She tells Shaun that we are all making her life living hell. Her txts are so incredible, so full of shit. I've taken photos of her emails sent to and from Shaun, from their work computers. He's not allowed to access internet alone. Oh yeah, it's her ex boyfriend Jordan, that is the father of Max. We only found out a few months ago. Nic said to Shaun that Jordan, had punched my mum, or that mum was throwing things at Max. All these lies. To make us sound like WE were incapable of looking after him.

I don't really talk to my sister anymore. I have lost her as a friend as well. She makes me sick. And she's sitting in the opposite chair at the table right now.. She's only been home for a few hours after six days away. As much as I love baby, I'm so tired. Mum is tired. I just want it all to end. Max will have no idea who his mother is. Everyone jokes that he will think it's me, we are inseperable. If she could only get her to talk to us, we could help her. I just don't think this is post natal depression, there is really something wrong with her. Living in all these lies.

One day, she'll run away and she'll die out there, alone. And we won't know. I tell mum she needs a counselor, or something. But she won't do anything. "At least she's home now." will be her reply. I know that mum is just relieved that Nicole is still alive. She is diabetic, and hasn't taken her drugs since Max was born. That's how slack she is.

Nothing we say helps. I just don't know what to do anymore.