My girlfriend owes me four dollars, and according to her tone, she is not going to pay it back. Should we break up?

Points, you don't like her, no feelings, it is not love, break up; Anyway, men should not pester women on trifles. In view of your situation, you'd better follow your own feelings. Since your initial definition is girlfriend, it is not a question of money. If you don't feel it, divide it. If you feel it, let's go together.