@Jamesy89,
Because:
- she obviously didn't want to talk to you
- yet most people, even if they don't like a person, aren't rude when that person goes out of their way to say hello to them
- that leaves them being wierded out
At the end of the day, it's just a guess based on how most women react.
Why is it a big deal? She doesn't like you, for whatever reason. We can't please everyone all of the time. Not everyone will like us, no matter how hard we try.
Hopefully you like you for who you are, rather than what everyone else thinks. If not, work on it
And move on.