I was convinced of this too (in fact I still think so, he is infamous for flirting a lot and had the distance to do it, although I'm not sure this was all it took for him to leave), but she herself said that she doesnt think that fwiw.
I agree that in most other seperations I would suspect that the woman only appears crazy because she was very badly fucked up, but I have my doubts on this one simply because it's very in-character for her (although there is always a chance that for once it's not that)
as for the daughter: he was barely home the past couple of years and he hinted at cracks between him and his daughters relationship because of that, especially the elder one (who is not seeing him). With her being the primary caretaker parental allienation should happen fairly easy. Plus it's not like the daughter doesnt want to see him: she just wants at their home (and we know that Alice for some reason wants him there too), which I somehow cant imagine can be the way a kid voluntary thinks. And if so it's quite worrying that she has already learned how to apply emotional manipulation :/
But yeah, there is every chance that your suggestion is on the money. I'm personally still convinced that both in one way or another fucked up