The American Reunion star - who competed on Dancing with the Stars in 2008 - said that she is in awe of Jenkins's drive and determination.
"I watch [Dancing with the Stars] sometimes. Now, I've gotta root for Katherine. I think she's gotta win it," Elizabeth predicted to Access Hollywood.
The actress added of her support for Jenkins: "[Jenkins] is really graceful and amazing and a wonderful dancer. And I love [her partner] Mark [Ballas], so I hope they win."
Jenkins also received public support from her former fiancé Gethin Jones, who praised the opera singer's "brilliant" dancing.
She is expected to take part in this week's Dancing with the Stars finale even after injuring her back during last week's performance.
Dancing with the Stars wraps its current season tonight (May 21) and Tuesday on ABC.
Watch Katherine Jenkins and Mark Ballas's semi-final salsa below: