How should I prepare for a 5k race?

Im taking part in the 5k bread and honey marathon (only 5k version though). My neighbour (who is a girl 3 years younger then me) is also doing it. I am a better sprinter then her 100% but she has done a 21k marathon before so she may be more prepared. I have about 2 weeks. I CAN'T lose to her (she is 15!) What should I do?