The 33-year-old Threesome star is playing the part of a laidback bride-to-be in a new comedy called The Stag.
Director John Butler says: "Amy is great -- a real professional. She's tiny, really petite. And in comedy it's all about the mid-shot anyway. There are no close-ups of people's stomachs. Usually."
The Stag is described as a cross between smash US comedy The Hangover and Deliverence.
So perhaps it's no wonder things got a bit messy on set.
"We were filming in and around the Sally Gap and it was the middle of winter, so things were never going to be pretty," John told the Herald.
"There was a lot of nudity, running up and down mountains naked, and lots of wild animals. All in a day's work." John co-wrote the script with Oscar nominee Peter MacDonald. "We got the idea because we were being invited to
a load of different stag parties," he said.
"The film is about a group of fastidious men who have no interest in going on a debauched stag weekend. It's really about masculinity. I think of it like an Irish version of Deliverance, except set in Wicklow, and without Burt Reynolds," he says.
Chocolat star Hugh O'Connor plays the uptight groom Fionan, while Sherlock star Andrew Scott plays the best man Simon.
Dublin native John first caught critics' attention when he directed RTE's acclaimed comedy series Yer Bad Self.
Sadly, there was no second series, but, since then, John has written a novel, The Tenderloin.
And his latest project is upcoming TV sketch show Immaturity For Charity. The comedy show will air on RTE2 on December 27 and features Love/Hate's Robert Sheehan, Brendan Gleeson and Killing Bono star Domhnall Gleeson.
"That was a lot of fun to shoot," John says. "All the sketches are filthy and juvenile and disgusting. So it's great TV."
John has released several clips from the programme online. One of the more popular clips is First Date, a sketch where Amy and Domhnall go on a nightmare first date.
After swallowing a pair of nail scissors, Domhnall asks Amy to try and fish them out of his throat before vomiting and bleeding all over her arm.
"Like I said, it's pretty juvenile," John said.