So I've got this friend who I have known for a little over a year now. He has a friend who he has known for several years. She met me, I said literally nothing and now she hates me somehow. It's tempting to just cut myself off from my friend and his friend because i don't want bad blood with them. But my friend is a neighbor who I would never be able to avoid completely. I don't want him to cut ties with her, obviously, but she hates a lot. Like, a lot. I honestly don't know what to do. Ideas?
Don't make a decision until you know the truth. Ask your friend what that girl really thinks about you and why. If you are braver, you could ask her directly. Maybe something you thought was harmless was offensive, and so you need to evaluate if the offense was justified (=need for apology) or not. Either way, your friend should know why the friendship is in jeopardy.