Did she have a couple of screaming toddlers in the back seat demanding their Happymeals? It might be justifiable windowcide.
Alcohol without a doubt.
I’ve seen something similar where a guy got out of his car and came out and slugged me. They refused his order in the drive through, and the guy jumped out of his car again, and grabbed the teller and tried to pull her through the window.
Next day the cops pulled up to his address and arrested him. He said he couldn’t remember a thing of what he did that night, and pleaded no contest.