"I thought he was very nice," she tells 48 Hours Mystery correspondent Richard Schlesinger. "He was dorky, but so many of us are. I mean, I can be a big dork, too. So, you can't hold that against him."
Houston first heard that her college friend had been arrested from another friend on the social networking Web site, Facebook.
"I logged on to Facebook and a girl that I hadn't talked to in about four years sent me a message, a chat message on Facebook, saying , 'Oh my God, Morgan.' And I started freaking out already because what is this girl going to say to me?"
It was the news that Markoff, the same man who just a few years ago was Morgan's classmate in pre-med, was now the nation's most famous murder suspect. When they were at the State University of New York together, Houston says she saw Markoff often.
"He was very intelligent," she says. "He was definitely lacking in some social skills. … It didn't seem like he was always 100 percent comfortable in his own skin."
Houston says she and Markoff were friends, but that was it. That was what she wanted, although she got the feeling Markoff wanted more.
Then, one night when a group of friends went out drinking, she says Markoff saw her to her dorm. She tells Schlesinger that along the way, Markoff cornered her, pushing her against a wall in an attempt to kiss her.
"I was turning my head to the side so he couldn't and I was saying, 'No, Phil. You know, we're just friends. What are you trying to do?' And I was trying to push him away. And he was being forceful," she recalls. "I couldn't physically get him off me… thankfully, one of my very close friends… had come along and he was able to pull him off of me."
Houston says she escaped upstairs, but felt shocked and betrayed by her friend, "…because, you know, I never gave him any signs that, 'Hey, Phil, I like you more than a friend.' It wasn't just the two of us out for drink. A lot of us were out. I was just hurt by it. And I just wanted to forget it. I knew he had a lot to drink that night. And I just was trying to chalk it up to that I just kind of wanted to forget about it."
Being in that situation scared her.
"I had no control. I physically couldn't push him away. And anything like that is always, it's frightening. …you don't know how far they're gonna try - I don't have experience with anything like this… He wasn't listening to me when I was saying no."
When asked if Markoff ever apologized to her, Houston replies, "No, I'm not sure he never mentioned it… it was awkward. I just wanted to forget about it. It wasn't the Phil I knew. The Phil I knew was a nice, easygoing, a little but awkward, but a nice, easy going guy. I chalked it up to the alcohol."
They remained friends, but Houston looks back at that incident now and wonders: Could it have been a sign that Markoff had a secret side?
"If all this turns out that it's proven to be true, then I should have been a lot more frightened than I was," she says.
Dr. Michael Welner has consulted on some of the most complex criminal cases in America.
"As a forensic psychiatrist, I don't hear this as a person living two lives," he tells Schlesinger. "You wanna know what a double life is? A double life is another wife, kids in another town - a different set of friends."
Looking at the evidence, Welner believes Philip Markoff was not leading a "double life." Instead, for some reason still unknown, Welner thinks Markoff suddenly embarked on a crime spree.
"In my professional opinion, I'm seeing an individual who was in school, who was in a stable relationship where there's no previous criminal history. And there are three dramatic crimes in 10 days. That has the hallmark of a spree," Welner says.