Shamail Malek, now aged 18, had been invited by her to the event in St Georges Hostel in Wolverhampton city centre which continued until 8am on January 6 last year, a judge heard.
He was a member of a gang at the time of the offence and arrived at the hostel armed with a machete, the city's Crown Court was told.
The young hostess made sure the weapon was put in a safe place inside the flat, explained Mr Timothy Sapwell, prosecuting.
He continued: "When she wanted people to leave there was a dispute among some of the guests and the defendant warned in slang that he was going to stab them all.
"He was thrown out into the communal area by other people preparing to leave the party and went into a neighbouring flat which he emerged from armed with a knife."
He then started walking towards the other group and the hostess, fearing trouble was about to start, instinctively grabbed hold of the blade which was slightly withdrawn by Malek before pushing it forward, claimed the prosecutor.
The defendant was then knocked out by another guest, it was said.
The victim's right hand was bleeding heavily from the wound on the palm that severed tendons and nerves which had to be repaired through microsurgery.
She remains "petrified" of knives following in incident, she admitted in a victim impact statement.
Mr Simon Rippon, defending, said: "This was a reckless action. He simply removed the knife from her grip.
"There was one wound not two. He was 16 at the time - a child. He was part of a gang at the time which had older members but he is no longer gang affiliated and does not mix with those he did then."
Malek, from Lynton Avenue, Claregate, pleaded guilty to wounding and being in possession of a knife and was given 14 months detention in a Young Offenders Institution suspended for two years with rehabilitation courses and a four-month night time curfew.
Judge James Burbidge QC told him: "I am able to avoid immediate custody for you because of your age and lack of maturity. It two days before your 17th birthday and you have not committed any offence since."