You "fell for her immediately".
You added her to FB the "very next day"
You "chatted" every day
You gave your
You did all this after only meeting once.
You "comforted" her about her ex
You were the infatuated, flattering nice guy. You bored her to death. Your desperation was smothering and worst of all... you allowed your emotions to tell you how to handle and treat her.
The ex probably called her and said "Come to my place tonight, I want you" and she rushed over.
Women don' want "best buddies" to chat with. They want men who will bend them over and be manly with them. You weren't very manly, you were nice/
And you know where nice guys finish? Last.
Until young guys realize, being cute and sweet and "a little scared to talk to her" and being "nervous" and all that other wimpy sh*t does not work and begin learning to act like men, this will be your fate.