Origin: combination of the words "spit" and "bitch"
Current meaning: It's used to refer to someone you used to be really good friends with, but all your other friends tell you, "dude, that person is a bitch. They're rude." But you just laugh and go, "Oh, no! That's just their sense of humor!" Then one day you open your eyes and go, "Oh my God, they really are a bitch." Then you're never friends with that person again and are probably their enemy.
That girl is a spitch. She was my friend, but she kept telling me I was stupid. What a spitch.
Ew, I saw my spitch today. They looked like shit.
Everyone has a spitch.