"I like how he's evolved, he's growing up, he's doing his thing," she added, during her appearance on 4Music's Rock The Look With Rimmel London.
"I like his stance and how he carries himself."
Rita, 23, is currently single following her split from Scottish DJ Calvin Harris this summer. At the time, there were reports that her friendship with Justin was partly responsible, after the pair grew close while working together.
Meanwhile, this week Calvin hit back at his ex-girlfriend, stating on Twitter that he had a "damn good reason" for blocking her performance at the Teen Choice Awards this year.
Rita had told radio DJ Ryan Seacrest that the reason she pulled out of the ceremony at the last minute was because Calvin had stopped her from performing I Will Never Let You Down, which they recorded together while still a couple.
"I was supposed to perform," Rita said. "(But Calvin) wrote and produced the song…he owns the rights to it… so (he) has to approve anything TV-wise… He didn't approve the Teen Choice Awards."
Asked whether there was any unresolved bitterness between the pair, she added, "You should ask him. You write a song with somebody and I guess there's some stuff that comes with it."
The star admitted she was angry, but "more for my fans" than for "my own selfish reasons".
On Wednesday, Calvin responded. "You'll only know 1 side of the story RE Teen Choice awards because I choose not to talk to the papers about every aspect of my personal life," the 30-year-old tweeted.
"But just know I had a damn good reason."
Rita and Calvin dated for around a year, and I Will Never Let You Down was their first collaboration. But on 6 June, not long after the single debuted at number one, Calvin announced that he and Rita had "ended their relationship some time ago".
You'll only know 1 side of the story RE Teen choice awards because I choose not to talk to the papers about every aspect of my personal life— Calvin Harris (@CalvinHarris) August 13, 2014
But just know I had a damn good reason— Calvin Harris (@CalvinHarris) August 13, 2014
Five days later, she confirmed the news, tweeting, "I've had an incredible time w Calvin & I will treasure the memories… Life can only be understood backwards but it must be lived forwards."
She recently opened up about the split to Glamour magazine. "I'm gonna tell you the truth: I'm not doing too great," Rita admitted.
"I adore (Calvin) and he's such an amazing human being… It wasn't about 'us'. It was about the world we live in… We both work really hard. We're both all over the place."