It looks like Rachel's (and Beth's) mother is coming back to McKinley. Idina Menzel, who as Shelby Corcoran was revealed in season one to be Rachel's biological mother and went on to adopt Quinn's baby. Her guest spot on the first season was five episodes long, but she's currently in negotiation for a much longer story arch spanning 10 to 12 episodes of season 3. And  while the last time she was working for the enemy as the coach of Vocal Adrenaline, this season she'll be part of McKinley's faculty, giving her plenty of opportunities to bump in Rachel and Will. Whatever it means for the story, Idina is definitely a great addition to the vocal power of Glee.

Source: JustJared