"[Miley's] been experimenting with women and even brags that she's had threesomes ... she is definitely bisexual. She has women over to her house all the time and hooks up with them. Lately she is more interested in women than men. She was completely brokenhearted after Liam and is kind of over men for the time being. I wouldn't be surprised if a woman came out and said she has hooked up with her soon."

One of her trusted bodyguards recently revealed some of her dirty secrets to a European magazine, and now an insider says Miley's terrified a tell-all is coming -- one that could ruin her life.

"Engaging in bad behavior in front of people the way Miley does is like playing Russian roulette," an insider exclusively tells Life & Style. "It's just a matter of time before one of her so-called friends attempts to sell her out."