I can't answer all of the questions, but take this as you will(from my past personal experience):
She knows. She knows you love her. She doesn't care. She has your number in her phone in case she NEEDS something from you. And she called you at "random" this night because instead of messing around with everyone else trying to get a ride, she KNEW that you would drop what you were doing and come get her. Because she knows you love her. Even if you didn't tell her. She didn't call in the last 8 months because she didn't need anything that badly from you. Things like this will happen from time to time, seemingly at random until you either sack up and tell her how you feel, or you decide to be strong-willed enough to not answer her call. Change her contact info in your phone from Sarah to DO NOT ANSWER or similar. Take the energy you use on worrying over her and put it into something useful...like learning to shoot your gun(s) better or some other sort of training.
**I am not a licensed psychologist, I do not watch Oprah or Dr. Phil. I am, however, cynical of womens**
+1000!!! Read this post until it sinks in. You need to get this woman out of your life forever and not look back. It ain't there man, and it never was. CUT YOU LOSSES, bail and move on. If she ever contacts you again, just say you have moved on. Anything less and you end up a lifetime loser. There are many fine women out there, problem is it takes a little effort to find the right one for you. Start now!! Nothing like a relationship with a woman who actually cares about you to have you forget the other nonsense. You will NEVER get anywhere with this person, end it now!!!!