Symons recently returned to her role as Summer Bay's Marilyn Fisher and had hoped that Murphy would be cast as the dizzy blonde's British friend Mitzi.
The Australian actress struck up a friendship with Murphy when they worked on Emmerdale together and the pair are still in touch.
Speaking to PA, Murphy explained: "Marilyn's been in England and has a friend called Mitzi - [the producers] were looking to cast her and she said, 'You've got to cast my friend Sheree'.
"I think they are casting for her now but I've got a job and can't be coming over to Australia! She said the producer is keen to do something in the future."
Murphy, who will be seen making her debut in Hollyoaks later this month, added that it would "make sense" for her to pursue work down under one day as her footballer husband Harry Kewell is from Australia.