Cannes (France) (AFP) - Sienna Miller was such a huge fan of Kevin Costner's films when growing up that she named her pet rabbits after animals in "Dances With Wolves". 

Now she is starring alongside Costner in his ambitious film series "Horizon: An American Saga" -- a four-part project that he mortgaged his home to fund.

The first two instalments -- each some three hours long -- hit cinemas this summer, with the first released on June 28. 

Miller, 42, said she remained star-struck. 

"I'm a child of the 90s. I can still barely look at Kevin, because he was such a huge part of my childhood," she told AFP.

Costner's Oscar-winning "Dances with Wolves" from 1990 was "the first time I really had my heart broken by a film -- I was obsessed with it," Miller said. 

She had two pet rabbits named Two Socks and Cisco after the wolf and horse in the film. 

"Horizon" follows multiple characters and storylines on the violent frontier of the 19th century as European settlers took over Native American land, with Miller playing a woman whose family is attacked and faces a brutal struggle to survive. 

"I like to think I would be an OK frontier woman. I'm more outdoorsy than you might assume," she said. 

"But I don't think it would have been fun. I know Kevin says he wished he lived back then. I think it was a very difficult time to have been alive."

Miller was pregnant for the filming of the second instalment, which made the conditions even tougher.

"We were really out in nature. That was hard, because you're in corsets and it's boiling and there are scorpions and rattlesnakes. 

"I found earth, that red earth, in my hair for like a month. Up my nose, ears, every orifice. Well, not every orifice," she added with a laugh.

Only Costner knew she was pregnant during the second shoot. 

"I was feeling pretty sick. That corset was not my friend!"

'Horrific genocide'

Miller welcomed the chance to learn more about the history of the period.

"This country with an indigenous people who were exterminated violently, brutally, in a horrific genocide -- that isn't talked about nearly enough," she said.

"It's a bloody history and a gory history and a devastating history. But it happened. And I think to be able to look at it and not get too political, but just to show the truth of it, that's refreshing."

Speaking at the Cannes Film Festival, where "Horizon" got its world premiere last month, Costner told AFP he began working on the script way back in 1988 but could never find a studio to back it.

"But I loved it and so I decided I would write four, which is very American of me -- insane," he said.

Reviews so far have been decidedly mixed, however, with IndieWire calling it "the dullest vanity project of the century" while The Telegraph gushed over its "sheer, magisterial sweep". 

Costner says he has no concerns about bankrupting himself.

"What's the fear? If they take it away from me, I still have my movie. I still have my integrity. I still listened to my heart," he said.