There are a billion reasons.
the guy did her wrong in a big way and it's being paraded around her face on a daily basis. he completely ruined their family. she did nothing wrong.
she'd have a ton of money of her own if she just divorced him... and she'd make more money on a tell-all book... and she'd make more money on child support payments...
she'd never have to deal with his sleezy, lying, nasty ass ever again and have enough money to live comfortably.
i mean, seriously, why is she putting herself through all this?