How should you act when you meet a girl who ghosted you? Avoid her? Hold her feet to the fire? No... you must be COOLER than this.
Sometimes, a girl will ghost you.
Happens to everyone. Nothing to be ashamed about.
She was excited when you met her. Maybe she agreed to a date. Then when you got her texting, she flaked on you, or quit responding.
What do you do when you run into her again?
Do you bring it up?
Guilt trip her over it?
Use a little self-deprecation about it?
Pretend it didn't happen and things are fine with you both?
If you get the response wrong, you'll only confirm any skepticism of you she earlier had.
Yet get the response right, and you can make her want something to happen with you much more than she ever did before.