Susi Ganeshan directed crime thriller also stars Neil Nitin Mukesh and Puja Gupta.
"During shoots I used to get both mentally and physically drained. For every scene, I had to bring the demon in me, which is not my personality in real life," Ameesha said in an statement.
After reaching home, "I used to be so exhausted that I didn't have the energy to do anything," she added.
"Kaho Naa...Pyaar Hai" actress, who played positive roles in hits like "Gadar Ek Prem Katha" and "Honeymoon Travels Pvt Ltd", found it tough to be bad in front of the camera.
"This was the most challenging role for me. This film has a mix of emotions, it has adultery, blackmailing, love and passion," said the 37-year-old.
"Shortcut Romeo" is a remake of Ganeshan's super hit Tamil film "Thiruttu Payale" and it is slated to release June 21.