ELVIS PRESLEY’s grand­daughter RILEY KEOUGH has been reduced to tears on the set of the new “Mad Max” movie – because her co-stars are treating her like an outcast, say sources.

She’s heartsick over being “frozen out” by actresses Zoe Kravitz and Rosie Huntington-White­ley while filming “Mad Max: Fury Road” in Namib­ia, Africa, charges a pal.

The situation has gotten so nasty that Lisa Marie Presley’s distraught 23-year-old daughter “would walk out” if she wasn’t such a dedicated pro, according to her friend.

“Riley’s having a rotten time. She’s not fitting in and is incredibly lonely and homesick. Zoe and Rosie have only made things worse. Riley took a two-week break from the set, but she was absolutely dreading the thought of going back to Africa to resume filming.”

An insider on the set of the $100 million movie says tension is at a fever-pitch because Zoe, Rosie and Riley are in virtually every scene to­gether.

“They all started out as friends when the movie got underway, but now Zoe and Rosie have become close to the exclusion of Riley,” explained the in­sider.

“She’s got another two months to go, and no one knows how she’s going to make it. She talks about going home ev­ery day.”

Making matters worse, over the sum­mer Riley also had to deal with painful reports that her British fiancé Alex Petty­fer, 22, cheated on her with sexy lingerie model Chelsea Heath.

“It’s sad because Riley’s really such a sweet person,” said her pal. “She’s crying herself to sleep most nights. It’s really a shame.”