If you're really interested in this girl, try to sway her, don't let her sway you. Most Budhists (at least the ones I know) believe that Jesus was real. If this is her case, show her all the points in the bible that conflict with Budhism. A big one being John 14:6 "I am the way, the truth, and the life. No one comes to the Father, but through me.". This is one of the most important verses to use if she's one of those, "I believe all religions are right, just not right for everybody" kind of Budhists, since it expresses very explicity the exclusivity of Christianity. Use logic to explain that if this is true, then it's true, and there's only one way into Heaven. If it's not true, then Jesus is a liar, and his death would've meant nothing, therefore not all religions can be right if they all (and almost all do) claim exclusivity over the others.
I would be careful, considering you're rather young (hey, so am I), but I would study Budhism, idealy from a Christian perspective, looking for ways that you could (tactfully) debate this girl, and show her Jesus. One really good Christian author that writes on Budhism is Ravi Zacharias. He has a book called The Lotus and the Cross which is a fictional conversation between Budha, Christ and a random lady. He also wrote Jesus Among Other Gods, a very good book. If you're not the reading type, check him out on youtube. Just search for Ravi Zacharias. Ravi used to be Hindu, and Budhism stems out of Hinduism and mixes Taoism to a degree. He's well versed in the major religions of the world.
If you're really into the girl, try to add her to our ranks, but stay strictly platonic until she's a Christian.
