How would you create a wireless connection between computer and a dial-up internet line?

My sister wants to put a new computer with Vista upstairs but all her telephone lines are downstairs. She lives in the country and broadband is not available. Can you create a wireless internet connection between a computer and the telephone lines downstairs. We are trying to avoid drilling holes though her walls.How would you create a wireless connection between computer and a dial-up internet line?
the only practical way would be to buy one of those really long phone cords





wireless dial-up would be way, way too slow