If you want to work for UPS, little girl, or any other company in the world, you better learn to defend yourself. If you cant handle a guy coming on to you and defuse it if it truly happened, then you should not work at a male oriented company. Go to the mall, sell make up, you cant work here, or anywhere. You are not socially equipped.
She might try going to the store and buying a nice card to the effect of "let's be friends" and write a little message inside.
The message might include that she feels he is a nice person but is not interested in any romantic ventures. Include a passage saying that if he continues his unwanted advances that I (the girl) can and will contact your boss to discuss the issue.
Don't go off half-cocked and get the driver fired. Have the common decency to give the driver a chance to stop this behavior. This way everyone can gracefully bow out with a degree of self respect.
Hand the card to the driver and ask him to read it when he gets back to his truck.
I bet that will correct the situation.