Miley Cyrus keeps geting more and more bad news. New details have emerged about her fiance Liam Hemsworth's rumored affair with January Jones, and they ain't pretty.

An eyewitness to whatever went down dished some new dirt to Life & Style (via WetPaint), and it sounds like Jones was all over Hemsworth, who was trying to be a bit more discreet. The fact that she was rumored to be inebriated likely played a factor.

"They went to a private house party, and right in the middle of the party, January was clinging to Liam, saying, 'You're so handsome,'" the source said.

Dude, we agree, but who says that anymore? "You're so hot!" sounds more plausible, doesn't it? Unless the whole 'Mad Men' thing is seeping from fantasy to reality. But we digress.

"He kept saying, 'We can't do this here,'" the source continued. "Then they left holding hands and went out in the hallway and were making out. She was wasted. It wasn't good."

A pal of Miley added, "Miley is freaking out. She's been telling her friends that she trusts him, but if she finds out the cheating claims are true, their engagement is over."

Jones wouldn't comment when asked about the cheating allegations, and neither Cyrus nor Hemsworth's reps have said a peep. Cyrus initially said her engagement is still on ... but her engagement ring was then off.

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