My ex had inappropriately searched things on his computer and had some pretty disgusting pictures on an encrypted/hidden file list. He also had Tor which I didn't know at the time as this was 2007 and when I was 17 but this can be used to access the dark/shadow/deep web.
At the time I had told him to seek immediate therapy or I'd never speak to him again. He promised he would but after a month he hadn't so I cut him off he also cut me off for nagging. I gave him the chance because he had said he was abused as a child by a family member and he also felt suicidal..
Since I'm sure he hasn't changed his spots, dated a 15 year old when 21 / 22 and posted a video of me online / shown to my male friends (I was 17 at the time).
Lots of people know what he did but stayed friends with him and that shocked and disgusted me.
OK yes I'd given him a chance but that was due to feeling he had a psychological problem not ignorance. When I realised he wasn't going to seek help I was out of them, suicidal or not.
But he'd even make comments in front of his male friends and they'd just respond 'that's just X for you'
I just never understood it so completely get your outrage. This guy has actually been convicted so you know he's deliberately been searching for this stuff.
I suppose she must be either insecure and feel nobody would want her (perhaps he's manipulated her to think so) or maybe she feels she's made her bed and now has to lie in it.
Either way she should've thought further than herself - those poor, poor children 
I expect many are going to keep her at arms length now, especially if they have children of their own.
Paedophiles are a very hard conversation to have.