Diddy's Ex-Assistant 'Mia' Testifies He Allegedly Sexually Assaulted Her

One of Diddy's former assistants says the music mogul sexually assaulted her for the first time during his birthday party at a swanky hotel in New York City ... but she says it didn't end there.

The witness, who is testifying under the pseudonym "Mia," told jurors she was working for Diddy in 2009 when he sexually assaulted her at The Plaza Hotel in New York, where he was celebrating his 40th birthday.

Mia said Diddy rented out the penthouse for a party filled with unnamed celebrities and she says he asked to speak to her in the kitchen, clearing out the room and leaving just the two of them alone.

She testified this was early on in her employment, and Diddy told her they were going to be working closely together and poured some vodka shots. She said she took the shots but they hit her harder than normal, and her eyes lost focus.

Mia told jurors Diddy got close to her, put his arm up the side of her dress, and kissed her ... testifying she didn't want him to do so. She says she wasn't able to say "No" because she was shocked and couldn't process what was happening.

She says the next thing she knew, it was the following morning and she was in a chair in a different room of the penthouse.

Mia testified she thought Diddy would never do something like that again and that it was all a huge accident ... but she then told jurors there were additional instances of sexual assault during her time working for Diddy.

She said the next time Diddy sexually assaulted her was at his home in Los Angeles ... she said she was sleeping in her room and felt the weight of a person on her and it was Diddy.

Mia testified Diddy used one hand to undo his pants and penetrate her ... she says she froze and it all happened very fast and she felt terrified, confused, ashamed, and scared.

She told the jurors the next time she was sexually assaulted was at a different Diddy residence in Los Angeles ... she said she was in his bedroom closet on the floor putting things in a bag and Diddy was in the closet. She said he took his penis out, grabbed her head, and put it in her mouth.

Mia cried on the stand as she testified and told jurors she was frozen and didn't do anything ... and said the incident made her feel like trash.