FAQ for
"90210" (2008) More at IMDbPro »

Check IMDb's soundtrack listings, or an alternative site such as http://TVShowMusic.com/shows/90210.

The answer is yes. It was confirmed by ET and in the pilot that she was Kelly's sister, and since her mother had a baby with David Silver's dad it's clear that Erin is Kelly and David's sister from the original 90210.

The character of Hannah Zuckerman-Vasquez was briefly introduced as a reporter on the campus news station right at the beginning of the first episode. The teacher, Mr. Matthews, turned off the TV with a throw-away line about the girl looking 30 (probably a reference to Gabrielle Carteris' being so much older than the rest of the original cast). Since then, she hasn't been seen on the show at all.