Are you absolutely certain about this? If your decision to withhold a reasonable tip for the girl isn’t due to financial hardship, it reflects poorly on your character and behavior, or worse, could be viewed as exploitation.
As a man, especially an adult, if you’re short on money, the solution is to go out and earn more—not to pinch $10–20 at someone else's expense, especially a lovely girl’s. Actions like these only lead to a loss of respect from others. You should take a moment to reflect on your behaviors. Instead of spreading joy or kindlness, you’ve only caused trouble, man. Honestly, I’m ashamed on your behalf.