Bosses say the move is designed to ready the paper for its next marketing push.
The Sunday edition of the Morning News hit the streets on 22 June with seven new editorial roles created ahead of the launch.
Editor Bill Martin said: “Feedback we have had from readers and advertisers has been overwhelmingly positive and we want to accelerate our drive to grow the South West’s own quality Sunday newspaper.
“We feel that in order to ready the newspaper for the next phase of development it requires a dedicated focus, Lisa will bring exactly that.”
Devon & Cornwall Media managing director Mark Sainsbury added: “We are very proud of what we have produced so far and the Sunday title is still evolving and being refined to make the newspaper and magazine even better for our readers.”
Lisa informed staff at the Barnstaple-based Journal of the move earlier this week.
No sales figures for the Sunday edition of the Morning News have so far been made public.
According to its most recently-audited ABC figures, the daily title has a circulation of 26,699.