She was at times combative with the prosecutor and revealed to jurors that she and Murray currently live together. Alvarez said she and her newborn son at the time had planned to accompany Murray as he traveled with Jackson for the singer's 50-night comeback tour dubbed "This Is It."
Alvarez told jurors that she received several packages for Murray beginning in April 2009. Prosecutors contend those packages contained propofol and other sedatives.
He said "that he was going to be receiving something, that if there was knock on the door, it was going to be a delivery that I could retrieve it for him," Alvarez said.
She claimed that she never opened the packages or asked about their contents.
Alvarez met Murray in 2005 at a Las Vegas club. In 2008, she testified that she learned that Murray was Jackson's doctor. She also met the singer.
"It actually was a surprise … he [Murray] said he wanted me to meet someone, so I didn't know where I was going and that was what happened. I was speechless when I met him. I couldn't believe I was meeting Michael Jackson," she said.
In March 2009, she gave birth to a son and Jackson took an interest in the child, requesting visits to see Alvarez and the boy.
"Michael was very interested in the baby … he wanted to schedule visits so that he could see my son," Alvarez said.
Alvarez told jurors that between April and June 2009, Murray would leave at 9 p.m. for Jackson's home and return in the morning to her Santa Monica, Calif., apartment.
"In the beginning when he was working for Michael, he would come back really early … and then it became later and later," she said.
Alvarez, an actress, said that Murray paid her $2,500 monthly rent. She said that even though he was paying her rent, she was still working as an actress.
"As a professional actress, my daily duties consist of maintaining my instrument … Acting is a little bit different than a 9-to-5 job … as an actor, your instrument is yourself," she said. "I was working, I was auditioning and I believe I had at that time, I had several national commercials at that time on air."
Two more of Murray's girlfriends also testified. One was working at a Houston steakhouse when she met Murray in 2009. She received a call from the doctor at 11:51 a.m. on June 25, 2009, less than half an hour before a frantic Murray called Jackson's personal assistant and screamed for help at Jackson's chef.
"What he said to me was, Hello, it's Conrad Murray, and he said, How are you doing. I said, Hello, how are you?" said Sade Anding. "He just said, Well, and then paused."
Anding said that she interrupted him and talked for an additional three to four minutes before realizing he wasn't listening.
"I realized he was no longer on the phone… I said, Hello, hello, and I didn't hear anything, that's when I pressed the phone on my ear and I heard mumbling of voices… I heard coughing and nobody answered," she said.
When Los Angeles detectives reached out to Anding after Jackson died, she contacted Murray for help.
"He told me, What, why, why are they calling you? I'm so sorry that they're contacting you and now you know, now you're in this. I'm going to give you my lawyer's number and make sure before you speak to LAPD, you have my lawyer present," Anding told jurors.
A third girlfriend, Michelle Bella, testified about meeting Murray at a Las Vegas club in February 2008 where she was working. Murray sent her a text message on the day Jackson died.
The contents of that message were not revealed.
Murray's one-time girlfriend Bridgette Morgan told jurors Monday that she called Murray on the day of Jackson's death, but that he didn't pick up the phone.
ABC News' Christina Caron contributed to this report.