Is it normal that I feel this way?

My sister just got her own place for the first time, and I'm really not cool with it. But not because I don't want her to move forward with her life, but she waited several days to tell me (and we're the type of close sisters that family shows like Gilmore Girls and What I Like About You have), moved in with a friend whom I don't think is a good friend to her and I've told my sis I can't stand her (thus making it less desirable that I hang out at my sister's place), and is asking everyone but me for help, including our abusive parents. She was sent to a lockdown boarding school last year and I didn't get to have any contact with her, and this fall she's leaving for college. Is it wierd that I'm having a hard time handling this, or is this something many people go through?