Cobb got her start in theatre at Cedarville University. She then attended AMTC and moved to LA and starred in local productions of Othello, Spring Awakening, and The Merchant of Venice. In 2009, she received her first screen role as AJ in the 2010 Disney Channel original film Starstruck. She also had small role in the 2009 film The Missing Person. Her other acting credits include The Mentalist, Jonas L.A., Medium, CSI: Miami, Pair of Kings, Imagination Movers, Big Time Rush, American Horror Story and the Disney Channel original film Good Luck Charlie, It's Christmas! (2011).
In 2011, she had a recurring role as Emily Bradford on The CW series 90210. She nearly did not receive the role, due to her resemblance to fellow 90210 actress Jennie Garth. They dyed her hair a dark color so it would make her look less like Garth. In 2011, Cobb wrote her first book entitled Stuck on a Ferris Wheel, a guide book to assist up-and-coming actors. As of 2012, Cobb currently has a recurring role as Kimantha on the ABC sitcom Suburgatory. As of 2015, Cobb booked a pilot called Cheerleader Death Squad.
- She became interested in acting after watching a Shirley Temple movie marathon in the third grade.
- Cobb portrays Jennie Garth in the Lifetime made-for-tv film The Unauthorized Beverly Hills, 90210 Story.