The Catherine Hardwicke movie follows two pals as one, played by Toni, undergoes breast cancer treatment and her best friend (Drew) struggles to fall pregnant.

The Sixth Sense star, 43, reveals the chemistry they created onscreen was very real because the two actresses really hit it off - and even headed off on holiday together as soon as the shoot wrapped.

"We got lucky, you can never determine what the chemistry is gonna be like, and this is a story about lifelong friendship," Toni tells U.S. breakfast show Good Morning America. "These two girls (characters) know each other inside out, they just get each other on a very basic level, and Drew's so grounded and she emanates warmth. She's the ultimate girl's girl and I can't imagine doing the movie with anyone else.

"We finished the movie and everyone's like, 'How did you feel (when) you had to part?' We were like, 'We didn't part, we took our families and went to Paris together!' I just love her, honestly... Not only was it one of the best working experiences of my life, but I came away with a really great new friend."

Toni recently revealed she reached out to Drew, 40, in the form of a love note in an effort to persuade her to sign up for the movie - even though she didn't personally know the Charlie's Angels star.

"I knew Drew was the ultimate dreamy best friend," she told "I basically sent her a love letter trying to convince her to come and do it."

Drew was moved by the sweet message and the film's script and decided to head back to work earlier than expected after giving birth to her second child, daughter Frankie, in April last year (14).

"I respect Toni so much, I just love and appreciate what she does," Drew explained. "I read the script and it really moved me. I just had my second daughter but I had to go.

"When I showed up, I told Toni up and down, left and right, that I was there to 100 per cent be her support system, which I felt was very fitting for our characters. Things just took off and we got along so well, which behooved the movie because these girls just have great chemistry. We tried to tackle a tough subject in a unique way that was told in a very lifelike tone."