Dunnett bought them three bottles of wine, then tried several times to touch her, including rubbing her leg and placing his hands around her waist.
She told the court Dunnett later pushed her against the fridge and said "yay or nay".
"He said he wanted to show me something [downstairs]. I was frightened and scared that if I didn't go downstairs with him what might happen and scared about what might happen if I did.
"When I was down there I felt trapped. He pushed me up against the bunk beds and tried to kiss me and stick his tongue down my throat. I was crying, and really upset, I was in shock."
She claimed Dunnett told her: "I want to make you feel fantastic."
The teenager pushed Dunnett away as a friend opened a door, before she ran away crying.
She went to sleep but woke to find Dunnett behind her. He had a hand down her pants and the other on her bra.
"As soon as I realised he was behind me I yelled 'f*** off'."
The next morning Dunnett apologised for his actions but ... "it was like he was making a mockery of what happened."
Earlier in the day another complainant gave evidence about an October 2011 party, also at the Ocean Beach Club.
The teenager admitted she was "trying to get drunk" but didn't ask Dunnett to "f*** me" up to 25 times, as defence lawyer Jonathan Krebs suggested.
"I drunk my [wine] bottle pretty fast, and did shots."
She said some of the night was "hazy" and parts of the night she couldn't remember at all.
Later that evening she was having sex with a boy and noticed Dunnett in the room.
"I said 'what are you doing here?' But I was pretty drunk so it didn't really faze me."
The witness then recalled standing naked outside, covered only by a sleeping bag, before she began talking to Dunnett in the lounge.
"I remember him kissing me, I don't remember how it happened ... He picked me up, carried me downstairs to the bedroom, shut the door and I assume he was trying to touch [me]. By this time I was wearing my dress again, I'm not sure how, but he touched me over the top of the dress."
She could only remember locking herself in the lounge and placing a bar stool against the door, "laughing and taking photos" because "it was so funny".
"I remember texting [my friend] and saying there's a scary guy trying to rape us out here."
When she woke her "best friend" said Dunnett had been touching her during the night.
Mr Krebs suggested during cross-examination that because of the teenager's "drunken state" she had "re-created episodes which did not occur".
She also denied lifting her dress and asking Dunnett to have sex with her multiple times, as Mr Krebs suggested.
But later added "there is no way I can defend myself because I can't remember" and "anything could have happened".
She said the moment Dunnett said "I'm a cop, no one is going to believe you, you are a little drunken girl," was stuck in her memory.
Dunnett denies saying those words, or words to that effect.
The Crown alleges Dunnett committed the offences while he was a volunteer lifeguard director and coach at Ocean Beach between May 2011 and New Year's Day 2013.
Further Crown witnesses are expected to give evidence today.
Dunnett is still employed with police but is suspended on full pay. He is also expected to give evidence later in the week.
The trial, before Judge Les Atkins QC, continues.
