A source told People that Cyrus, 26, "doesn't want a serious relationship."
The insider added, “She and Kaitlynn spent every day together and it just [wasn't] anything that Miley wanted to continue doing. She wants to focus on her career.”
A source previously told People that the pair are still close, though they're no longer romantically involved.
Carter, 31, and Cyrus hooked up in Italy just hours before the "Wrecking Ball" singer announced her separation from husband Liam Hemsworth — and just weeks after Carter and Brody Jenner ended their own relationship, which was been rumored to have been an open marriage.
It was later revealed after Carter and Jenner, 36, split that they were never legally married despite having a wedding ceremony.
A source previously claimed that Cyrus' flagrant PDA with Carter put the final nail in the coffin for her and Hemsworth's eight-month marriage.
“He thought they could work it out, but all those pictures of her and Kaitlynn ended that,” the source explained. “Liam comes from a very conservative family and his family was freaked out by it.”
Reps for Cyrus and Carter did not immediately return Fox News' requests for comment.