She might be a right nutter, ghosting is fine if someone is a hysteric, or a testeric, or dangerous or just a total unflushable who won't take no for an answer. You're not owed an exit interview and sometimes people ghost to preserve their own peace. And the reality is, almost nobody ghosts anyone if they have another choice that won't cause them a lot of misery. Occasionally yes, but not often at all.
Also, she is complaining publicly about being dumped months and months after he dumped her, which honestly looks like she's an unflushable. For all we know he tried to tell her umpteen times.
But yeah maybe he's an arse, there's no way to tell. Her only option is to get on with her life, regardless, you can't make people love you or do anything at all really, unless they want to.