(Reuters) - A California state appellate court has revived celebrity personal trainer Jillian Michaels' lawsuit against Greenberg Traurig over its alleged bungling of branding contracts for stars of "The Biggest Loser."

A three-judge appellate panel faulted Los Angeles County Judge Mark Young for excluding an expert witness's report that determined Michaels lost millions of dollars after she signed two conflicting contracts the law firm should have warned her about.

Young scrutinized the expert witness's estimates too harshly, the panel found in its Friday ruling, noting that at this stage in the proceedings, the judge was required to view Michaels' claims in a light that heavily favored her.

The panel, led by Associate Justice Sam Ohta, revived claims of legal malpractice, breach of fiduciary duty and contract and negligent misrepresentation against Greenberg Traurig and her former attorney David Markman.

"We are overall pleased that the court of appeals reversed the superior court decision, and look forward to now trying the case on the merits," Michaels' attorney, Richard Busch, the head of the entertainment and intellectual property sections at King & Ballow, said in a statement.

Michaels was featured as a trainer on 12 seasons of "The Biggest Loser," a reality show that featured overweight or obese contestants competing for money by losing weight.

Her 2009 contract with the show, negotiated by Markman, placed restrictions on her ability to do commercials. However, Michaels and her company, Empowered Media LLC, then signed a contract with dietary supplement company ThinCare International LLC.

Michaels' contract with ThinCare provided her with a $2 million royalty advance, as well as a sliding scale for more royalty payments. ThinCare paid Michaels' Empowered more than $5.5 million over the lifetime of the agreement.

Michaels alleged that Markman and Greenberg Traurig did not advise her that the two contracts conflicted with each other, leading to ThinCare suing her in 2011. Two and a half years later, Michaels and Empowered paid ThinCare $2.2 million, forfeited nearly $1.3 million held in escrow, and agreed to not be paid royalties for nearly three years.

Michaels' expert estimated that she lost out on $7.3 million and $11.5 million in royalties as a result.

"We acknowledge, evidence within the record reveals Michaels was unhappy in her dealings with ThinCare prior to the ThinCare litigation," the panel wrote. "However, in a summary adjudication motion, the trial court does not weigh the evidence."

Greenberg Traurig and Markman, now the co-chair of DLA Piper's entertainment transactions practice, are represented by a team of attorneys from Jenner & Block. Neither a spokeswoman for Greenberg Traurig, the firm's Jenner attorneys or Markman responded to requests for comment.

The case is Michaels v. Greenberg Traurig LLP, California Court of Appeal, Second Appellate District, No. B300093.

For Jillian Michaels and Empowered Media: Richard Busch of King & Ballow

For Greenberg Traurig and David Markman: Michael McNamara, Kirsten Hicks Spira and AnnaMarie Van Hoesen of Jenner & Block