It would be nice if she showed up or gave you heads up but that didn’t happen. I’d try not to be overly upset especially since she did reach out and apologize

I’d say since you don’t really know her well (only met once at an event awhile back and after that just communicated on FB), you don’t really know what’s going with her. She might not be comfortable to share but maybe she had a panic attack, upset stomach, marital problems, work issue, was depressed about something, her house was too messy for virtual chats, too tired, was wearing a pajama, didn’t take shower today and hair was messy, had a fight with her cousin, reprimanded at work etc

Ton of things could happen that prevents one from joint virtual chats especially with almost strangers. I spend a lot of time on virtual platforms and know how many people are uncomfortable especially doing it from home

Now if it was close family member or long term close friend, I’d see how it’s hurtful but this person seems to be an acquittance rather than a real close friend who owes you an explanation .