Wendi told the Herald how she fell in love with the character who was abandoned by her husband, leaving her to take care of her children.
"When I got the script I just couldn't put it down. I felt such empathy for the character."
"She's had a hard life which is interesting for me to play, instead of me being the one giving the bad luck," she jokes.
Wendi is performing for eight weeks only in Ireland:"The reason it's split is I didn't want to be away from my eight year old [Grace], who's on the plane coming over from Heathrow for the weekend."
Wendi says her version of the character will have an English accent and Mary's will have an Irish one.
"I wouldn't insult Dublin that much by putting a Dublin accent into it," she jokes.
Wendi says audiences are responding really well to the new version.
The play's director Michael Scott says the two actors and Cecelia re-worked the play to make it more real for its audience.
"With Wendy and Mary and Cecilia we've worked to put a few changes to it. We've put an interval in the show and have a completely new set and new costumes."
He added: "Audiences are going mad for Mary and Wendi. Tthey've both got a real hold of it."