She returned to California after the start of World War II and enrolled at the Chouinard Art Institute.
In 1948, her design for a white fleece overcoat, electrically heated by batteries carried in two side pockets (with an extension cord that could be plugged in on planes or trains), was featured in a futuristic fashion show sponsored by the Los Angeles Fashion Group.
[2] In 1951, Lucille Ball approached Jenssen and asked her if she would be interested in designing costumes for a new situation comedy she and her husband Desi Arnaz were readying for CBS.
Under exclusive contract to 20th Century Fox at the time, she was unable to accept the offer, but after leaving the studio to freelance, she spent a season designing clothing for Ann Sothern on Private Secretary, then contacted Ball to see if the position on I Love Lucy was available.
[3] Her later television credits included designs for Julie Newmar in My Living Doll and Eleanor Parker in Bracken's World.