Drunk at or behind the bar?

The owner fired a coworker today. Apparently she showed up buzzed at 4pm on Wednesday (Thanksgiving Eve), and by the time I got there at 9pm I heard she was decently drunk. Within 5 minutes of my showing up at work, I saw her break a glass, almost spill a drink, and knock over the pen holder. I found out later she had also slipped the waitress a whiskey&coke for free. I guess she wanted someone else to be as drunk as she was. Needless to say, she was asked to go home for the night.

Friday she shows up at the door, and the owner goes to talk to her. Apparently he asked her to not drink excessively behind the bar and she defiantly told him it was her right to, and also it helped her be a better bartender. The owner got pissed and fired her. I guess both of them could have handled it in better ways, but it's over now.

So I filled in for her on Friday and worked with a girl I've never worked with before. She was drinking tequila shots throughout the night behind the bar as well, but did it more discreetly and didn't get drunk enough to be clumsy all over the place.

Anyway there are a couple of points I found interesting. Why would the owner fire someone for drinking behind the bar when others are doing it too? I guess she just handled it the wrong way. And she also slipped the waitress that drink, which I guess was the final straw for the night.

Isn't it illegal to drink behind the bar in Philadelphia anyway?