The actress explained that she had "put to sleep" her character Saffy, the daughter of Jennifer Saunders's Eddie Monsoon, before the BBC series was revived for three specials.
Asked for her thoughts on next week's Olympic Games episode, Sawalha said: "I really had so much fun making this special, especially given I was reticent about the idea of doing more Absolutely Fabulous.
"I had put Saffy to sleep and I know it sounds all actressy to say this, but I wasn't sure if I could climb back into her skin.
"But as soon as I knew everybody was on board and I became aware how excited Jennifer was about it, everything started to click into place."
Sawalha went on to praise her other co-stars Joanna Lumley, Jane Horrocks and June Whitfield for their humility on set.
"What I love about doing Ab Fab is there are no egos to battle with," she told The Mirror.
"We have huge respect for each other and there is so much generosity and support. That is quite rare on a show."
The first pictures from the Absolutely Fabulous London 2012 special - the final of the planned 20th anniversary shows - have now been released.
Ab Fab's 'Olympics' airs on Monday, July 23 at 9.30pm on BBC One.
Watch Digital Spy chat to Joanna Lumley about the episode below: