This girl is creeping me out at work

This girl has been very flirty with me out of nowhere the past few shifts. I just shrug it off and ignore it. This is at kfc btw not burger king cause i always got something to say about burger king. Anyway im working on the chicken and she asks how old i am before i can answer she says to let her guess. She kept lowballing her guesses. Eventually i tell her my age and she's shocked saying i dont look that old. I made a vampire joke and she went away. She came back after when i was about to leave for th3 day and she said she's 18 just turned it.

Needless to say i feel uncomfortable. I knew she was young somewhere between 18 to 20 but just turned yikes. Granted i know she is technically an adult but she really has no business trying to hit up someone my age. No wonder why it made me uncomfortable from the get go