Udy stayed the night and left in the morning. Several days later, his victim laid the complaint.
Udy pleaded guilty to threatening to kill or cause grievous bodily harm.
He told police he knew he shouldn't have said what he did, but he didn't mean it, Ms Willemsen said.
The victim, who is no longer with Udy, asked for a protection order to be made.
Defence lawyer Anna Brosnahan pointed out the complaint was made on May 26 and Udy had been invited back for dinner in between the two dates.
"He accepts that his comments would have been extremely frightening," she said.
Ms Brosnahan said Udy had plans to become a teacher.
"Whether this interferes with that is a matter for another day," she said.
Judge David Cameron said the victim impact statement spoke of a "controlling" person.
Judge Cameron described the offending as a "nasty incident" and sentenced Udy to 80 hours of community work with six months of supervision. He also made a protection order in favour of the victim.