The Believe singer recently filed for a temporary conservatorship over Allman, 49, citing concerns about his health and finances.
She alleged Allman was "gravely disabled" and "has no concept of money", adding he "is unable to manage his financial resources and was unable to withstand fraud or undue influence" due to "severe mental health and addiction issues".
However, a Los Angeles judge rejected Cher's bid to appoint a conservator, saying she did not see "sufficient urgency", according to People.
Allman is an inpatient at a psychiatric hospital, as he faces criminal charges in New Hampshire.
Cher had claimed in her filing that any money Allman received from his late father Gregg Allman's trust was "immediately squandered" on drugs.
A new instalment from the trust is due in May, but the judge ruled that because Allman was in hospital with charges pending, she did not believe he would be able to access the money.
"These distributions have been happening for years, as I understand it," the judge said.
"So the fact that a petition was filed two weeks before the next distribution when that schedule has been known for a very long time doesn't necessarily qualify in my mind as an emergency."
However, the case has been dismissed without prejudice, meaning Cher can file again if she wishes.
According to court documents filed by Cher and obtained by People, Cher - who previously filed for a temporary conservatorship over her son's estate in 2023 - claimed Allman's life "has significantly deteriorated" since the last conservatorship petition.
Allman is facing charges after allegedly causing a disturbance at an elite prep school in New Hampshire.
Police were called to St Paul's School in Concord in February amid reports of an unwanted guest.
A spokesperson for the Concord Police Department told TMZ that the school reported an unwanted guest, who was allegedly "causing a disturbance and acting belligerently".
Allman is not believed to have any connection to the school.
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