As the night progressed, Alderman made romantic overtures towards the woman after joining her on a couch.
She rebuffed him and the defendant left the cabin.
When he returned he found the woman asleep on the couch, her daughter still in the bed.
Alderman slept on the floor for some time before getting onto the bed, lying behind the teen in a "spooning" position, the court heard.
He reached over her, pulled her close and began to touch her upper thigh over her clothing.
He then put his hands under the victim's top and squeezed her breasts so hard he left two small bruises.
Alderman's actions woke the girl, who used her elbow to push him away.
She fled the bed and tried to wake her mother but, unable to rouse her, got ready for school.
Judge Peter Rollo said the consequences for the victim had been "more than minor".
She now struggled with male teachers being close to her at school, he said.
Alderman said because of his state of intoxication his memories of the night were hazy but his counsel John Westgate stressed that should not be mistaken for a lack of remorse.
"That isn't an excuse, it's just an explanation," he said.
While Alderman had no sexual offending convictions on his record, the judge noted a criminal history seemingly driven by the misuse of alcohol.
He called the assault "drunken opportunistic touching" rather than a pattern of behaviour and opted not to add the defendant to the Child Sex Offender Register.
Alderman was convicted of indecent assault and ordered to pay the victim $1500.
