Nonsense.

When I was young I went out less often and to less expensive places. I most certainly didn't decide I could rob my server because I wanted to live high on the hog and then stiff the waiter or leave a paltry tip.

Also, it is quite obvious that this boyfriend wanted to take her out. This is not about her not paying the tip. I guarantee this boy would have a full blown tantrum at the dinner table if she tried to pay the tip.