Why Miley Cyrus broke up with new girlfriend Kaitlynn Carter

Cyrus' relationship with Carter lasted less than two months. Photo / Instagram

The reason behind Miley Cyrus' split from new girlfriend Kaitlynn Carter has been revealed, days after a video surfaced of the singer kissing Australian singer Cody Simpson.

Cyrus, 26, and Liam Hemsworth, 29, shocked fans in August by announcing they were breaking up after less than a year of marriage, with Cyrus going public with Carter just hours later.

Liam Hemsworth and Miley Cyrus split last month. Photo / File

Their whirlwind romance featured a PDA-filled Italian holiday, multiple dates in Los Angeles, and Carter supporting Cyrus backstage at the MTV Video Music Awards last month. But less than two months after the relationship was revealed, it's already fizzled out.

According to TMZ, sources close to Cyrus revealed the Slide Away singer called things off over fears it was moving too fast with her new lover so soon after the breakdown of her decade-long relationship with Hemsworth.

"Miley did not want to rush into anything. She and Kaitlynn have been close friends for a long time and things got romantic. Miley was ready to call it off because she wasn't ready for a relationship. She needs to be by herself," an insider told TMZ.

People magazine reports the abrupt decision left Kaitlynn "surprised and upset".

It comes after video emerged of Cyrus canoodling with Aussie star Cody Simpson, 22, in a Los Angeles grocery store.

Following its release, the singer took to Instagram where she penned a long post to set the record straight on her dating life.

"Men (especially successful ones) are rarely slut-shamed. They move on from one beautiful young woman to the next, most times without consequences … where women are called sluts/ whores," she said.

"I know the public feels invested in my past relationship because they felt like they saw it thru from the beginning.

"This dating thing is new to me too. I've never been an "adult"/ grown ass woman experiencing this … I was in a committed relationship for almost all my teens and early 20's, with the exception of a few breaks.

"I would like to share an activity with someone I am dating and not be stuck at home with nothing to do.

"Please don't make this awkward for me. I am trying to make light and like always make fun of myself … get used to me dating — this is where I am at! #hotgirlfall"

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Beanie takes Powell 🛶⛰🏞

A post shared by Miley Cyrus (@mileycyrus) on Sep 25, 2019 at 6:24pm PDT

In response to the TMZ footage, she posted part of it with a note saying: "Can a girl not get a f***ing acai bowl and a morning make out session in peace?!"

The Aussie singer and Cyrus have been close for years and have often been spotted hanging out.