Wow, I totally disagree with you.
I have had bad days and I can understand how they can affect you. So when I get a server who is having a bad day I can understand and relate. If I feel like a server is doing a bad job then I leave 15% and for me that is almost like leaving 50.cents. I have never understood. Would you want your boss to dock your pay if you had a bad day?
I think it's trashy that she is allowed to sit at the bar at all, let alone sit there the entire time chatting it up with the bartender and it's worse when it's in plain view of the customers. If she has a problem with the $$$ she's making, she's going to have to learn to work for it.
When I waited tables, you were allowed to sit ONLY when you were off the clock!!! Store motto was, if you have time to lean, you have time to clean!
If she can't take a refill to a table, or get the food to the table while it's HOT, maybe she should seek new employment and/or, report off the next time she's having a bad day.
Whining about how much money a table left where other customers can hear? Why is that acceptable on any level? Chasing down a customer who didn't tip you what you felt you deserved? That would be trashy coming from the waitress who just gave you the best service of your life, but it's so much richer coming from the whiner who sat on her butt and did nothing!