I'm really sorry this happened and I can see what an incredibly difficult situation it's left you in. I don’t know what I'd do if my son's nursery suddenly closed! (Well, it did during covid, but luckily I was working from home so could cope in the short term!).
The thing is, though, although it is rubbish for you, would you really expect her to miss out on a life opportunity for this? It's not fair, I know, but I've been in a similar position to her. I left a job I'd just started at for an amazing unexpected job (more than twice the salary and about 10x more prestigious). I felt really awful about letting my employer down, but I knew I'd regret missing out on this opportunity so much more. What might be a short term inconvenience for you might be the chance of a lifetime to her.
I'm not saying she's right, and it's certainly unfair. You have every right to be angry. But ultimately there's not a huge amount you can do. By all means, if asked for a reference in the future, mention that she did not serve her notice period. But honestly, this is just a risk that comes with childcare, unfair as it is.
Hope you manage to sort it. I've only skimmed the thread - did you say if you could work from home in the short term? Any family to help out?