I am prone to ruminating thinking, self-doubt, obsessive cycling (even though I can give out good advice, my darned mind isn't quite so easy to rein in).
All this investment in negative energy, combing over the past for answers, lashing out at people, will do Alice's health no good at all. If she's going on sites like Mumsnet (maybe even the DM) and "putting her side across" - it's just a waste of time and exhausting for her. We know that you can't win with trolls, you're better ignoring them, or better still, avoiding anything that triggers you. The internet is just too immense and ever-changing for you to challenge everyone that doesn't agree with you.
Honestly, if she keeps this up she might start moving on from reacting impulsively online to reacting impulsively in real life. And she could be in danger.
She's hurting, and that's okay, but I suspect she's more mentally ill (or at least, in a, hopefully temporary, downward spiral) that she really needs to call a halt on. Her oversharing and need for online validation has derailed her marriage and may now derail Alice's health.
I'm not a social media addict but I know how sick fixating over someone who has hurt or abused you, blaming yourself, hating the new person, hating yourself, re-living your time together - makes you become, if you get lost in that self-destructive bubble.
How does she even have time for her kids? Surely they should give you perspective and a welcome distraction from your misery?