Judge Emma Peters said: "Given the breach of trust here and the extended period of dishonesty, and the terrible fact that her victims were her parents, is clearly an aggravating factor in my view."
As Humphreys siphoned off money for months undetected, Christopher Baxton, prosecuting, explained the total figure could reach £200,000.
Humphreys denied a further three charges of obtaining property by deception, for which Baxton said there will be no trial.
Defence counsel Steven Levy called for an eight-week adjournment for a psychiatric report.
He said: "Clearly this matter was not one that was easy to assimilate because of the age of some of the offences and the defendant's parents went away some time ago.
"That has had a big impact on her, and her mental health."
In summing up, Judge Peters, said: "You've pleaded guilty to most of these offences and stolen tens of thousands of pounds from your parents, just short of £200,000.
"I don't want you to be under any doubt at all that the most immediate sentence will be one of custody."
She added: "Bail is no indication of the sentence you might receive."
Humphreys must stay at her home and surrender her passport to Colchester police station until November when she is due at Chelmsford Crown Court for sentencing.