I feel like this will be unpopular but here's my take:

The waitress was annoyingly proud of her self, but she wasn't exactly wrong. If you treat a stranger like an actual human you care about by engaging with them in conversation(and if you're in the industry you should be doing this-- it's basically half of the job, after all) that person will feel welcomed and noticed by you. In the US at least, that is generally reflected in the amount of tip money you earn. Like I said, she was obviously peacocking & that is annoying... but she wasn't wrong.

& you seem to be aware that tips are a large part (if not the majority) of her income.

You're both humans trying to exist and neither one of you treated the other accordingly.

ESH