I suspected it might be something like that.
It's absolutely not normal or OK ybder any circumstances to text an ex that they'll be alone forever because xyz. Especially at Christmas.
What an utter bastard.
It doesn't matter how 'unhinged' she is. Infact if anything, that's more reason for not saying stuff like that to her.
She says he ruined her life? Maybe he did.
He certainly says things I'd expect a sociopath or narcissist to say. Wouldn't be surprised if he abused her when they ere together too.
There are certain things that normal human beings capable of empathy do.not.say. to eachother, no matter the circumstances.
Abusers however...textbook for them to jump to 'everyone thinks xyz about you and you'll die alone'. I suggested it might be that even before you told us because that is absolutely a non negotiable thing for anyone yo say under any circumstances. And extremely indicative that you are dating a dangerous, yes, dangerous, person.
Trust your gut! Don't let people talk you into making excuses for totally abnormal and frankly, abhorrent behaviour.
Or next year, you'll be the 'crazy ex'.