This was the the Hollywood Reporter today. Although she's not a regular (as of now), it's exciting that she will be back on TV. And maybe if this show makes it, she become a main cast member later on.

"In the spinoff, Kelly is a guiding counselor at her alma mater, West Beverly Hills High.
Garth raised speculation about a possible stint on the new "90210" after she departed the CBS comedy pilot "My Best Friend's Girl" last month.
While she is not a regular on the new "90210," her casting still brings the new show closer to the traditional formula of a spinoff, which features a character from the original series.
The "90210" spinoff is considered a lock for a series pickup at the CW and is expected to be the central piece of the network's upfront presentation next week.
Gabe Sachs and Jeff Judah rewrote the pilot script and are exec producing the pilot. The two also are in talks to stay on as showrunners.
Garth, who also starred on WB Network's "What I Like About You" and on ABC's "Dancing With the Stars," is repped by Endeavor and James/Levy Management."</b>

You can find the article here:
http://www.hollywoodreporter.com/hr/content_display/news/e3i5e732e045deaaba3bfc4bc4e7f13d69d