The only thing Alice hasn't said as the vengeful ex-wife, is, If I can't have him, nobody can. She seems like a toddler having a tantrum - she bullied him out of the marriage and now wants to bully him back. But she didn't value what she had, anyway. Revenge is utterly pointless and, as others said, it doesn't change how he feels or what he chooses to do next.
I think some men like domineering women and it offers them a strange sense of security/familiarity, particularly if they're insecure at heart. Maybe she suited him 20 years ago but he's wised up to how controlling, destructive and erratic she really is. Strong personalities can be beguiling, but Alice obviously has a very dark side to her nature. This is not a normal or healthy reaction to a break up. He's wised up, he's gone and he won't look back.
I imagine Alice does have people trying to give her advice but if someone attacks you when you tell them what they don't want to hear - you have to let them learn the hard way.
Those girls should be removed from this situation. I think when Ioan returns things will change, big-time. It can't happen quick enough. Hopefully a gagging order, rehab/hospitalisation and sole custody for Ioan.