Runaway mommy

As mothers we've all had days where we've felt like running away and starting life over. While this is a regular thought process for me personally, it is certainly not something that I would EVER consider following through with.
Over the past few years I have actually heard of women who have gone through with it - they've left their families, found a boyfriend, and started life over with someone new, leaving the kids from the first relationship with their dad, along with full custody. Up until now the women I've heard about that have actually gone through with this have been friends of friends, but I have recently acquired a new hairdresser who has done exactly what I'm talking about.
Although I'm not sure of the details, approximately 3 years ago my hairdresser, mother of 4 kids - twin girls age 17, daughter age 12, and son age 8, (they were 3 years younger when it occurred) decided that she'd had enough of parenting, divorced her husband, and gave him full custody of all 4 kids claiming that she just wasn't cut out for parenting anymore. IS PARENTING A CHOICE? IS IT A JOB WE CAN QUIT? I THINK NOT!!!!!!!!!!!!!!!!!!!!
As a mother of a 7 year old, I can't even begin to wrap my head around making the decision to stop being a regular part of his life. It took me years to feel comfortable with the idea of going on a vacation without my kids let alone leaving them permanently. Until my kids were old enough to understand that I would actually be returning, I just couldn't bring myself to leave them for more than a few hours at a time. How does a mother do this?
My only conclusion as to how women can justify walking out on their families is that there has been some serious genetic malfunction in the structure of the woman involved's brain. How you can go through 9 months of pregnancy, countless sleepless nights, the terrible two's, numerous milestones, etc. , and then just decide you're done, is incredulous! My children are a part of me, and to consider the idea that my hairdressor's son at the young age of 8 has no regular female presence in his life to put on bandaids, to listen to all of the "unfair" things that happened to him at school from day to day, or just to give a hug when he's feeling down, makes me want to cry, yell, SCREAM! It is one thing to loose your mom in an accident or due to illness, but for her to "choose" not to be part of your life has got to be horendous!
I realize that there are fathers that do similar things every day. I realize that the loss of a father in this manner is life-altering as well, but I don't think it can be compared to the rejection of your mom, the woman that gave birth to you.
Like I said, my only conclusion is that these women are severely genetically mutated!!!!!!!!!!!!!!