ET also spoke with the former 'Dance Moms' star about her recovery after her spinal surgery.
"I'm very proud, I'm very proud," Miller, 55, told ET's Kevin Frazier, before being asked how hard it might have been for Siwa to hide her sexuality. "I don't think she hides anything really. I think maybe she just didn't know."
"I have a lot of students that struggle with their sexuality. I will be honest, mainly guys that dance for me throughout the years. Some have come to me and said, 'You know, without you, I would've committed suicide,'" she shared. "To hear that as a teacher, it is shocking and also very loving and kind and that I know that I did that for that child…And what you do in your private life is your business. But JoJo didn't really have a private life."
"Her life is for the whole world to know about. Every single thing that she's doing with social media now, everybody knows what we're doing and what we're up to at every moment. And we tell them, we share it," Miller continued. "So for her to make that statement and to share that, that's what she wanted to do."
Last month in an Instagram video, Siwa opened up about her sexuality, and thanked her followers for "the most endless amount of love and support."
"Somebody said, 'What label are you?' And you know, I have thought about this and the reason I am not ready to say this answer is because I really don't know this answer," Siwa told her followers. "I think humans are awesome. I think humans are really incredible people."
Miller added that she's "proud that she had the guts to do it," adding that Siwa has a great family.
"Hey, I'm single and sometimes guys are jerks. So good for her," Miller jokingly said. "And that's what I said. I said, 'You know what, JoJo, that's more hot young guys out there for me. That's good, that's good.'"
Miller, meanwhile, is a fan of her former dance student's mega empire.
"I don't know if she's just a marketing genius and we don't know this yet. I'm proud of her. I'm proud of everything that she does," Miller marveled. "She's shooting a movie right now in Canada. She has all these things lined up. She's great. And it's great energy to be around for me. It's uplifting and it's fun and it's positive and it's exciting and I like that."
Miller also values Siwa and her family's support throughout the years. In 2018, the dance coach was diagnosed with cancer during an emergency surgery on her spine. She's now cancer-free, but the recovery has been slow. Miller has been confined to a wheelchair for nearly three years.
Miller told ET that Siwa's family has been there for her through her health issues. "I've been to their home many, many times. They're there to talk to, they're there to call, and JoJo calls me and texts me with every exciting new thing that she has coming up," she shared. "So it's good to be involved, to be, you know, not forgotten."
Miller is on the mend now. The next step is to have her walking again after her multiple spinal surgeries. Dr. Hooman Melamed, whom she calls her "hero" and "superman," also joined Miller in the interview. He saved her life by discovering the cancer that other doctors had missed.
"They admitted me and within 48 hours I was paralyzed from the neck down," Miller recalled, with Dr. Melamed adding, "The cancer was unbelievable, how fast it had spread over 12 seconds."
"I always like to look at the glass half full," he continued. "I was optimistic that we were going to save her. That's how I always like to look at it."
Miller will continue to complete her physical therapy, but she still has trouble walking.
"I can do about 150 steps before I have to take a rest," she shared. "I'm putting so much weight and so much pressure into my arms to walk that I don't trust my legs because I can't feel the floor."
Tune in to Entertainment Tonight on Friday to hear more about Miller's recovery, the moment she thought she was going to die, and more.