After the pair advanced to the semifinals at the end of Monday night's Dancing with the Stars performance show, Alan also told Us of the affectionate pet name, "We say that all the time."
"I'm like, 'Babe, come on!'" Hannah explained to the magazine.
"We are, like, so close at this point. So he could... say anything, and I would be like, 'Whatever.' Like, we're just really at that point where we've spent every single day [together]. He's had to become my best friend. It's been great."
Alan added that he and The Bachelorette star have developed "a level of trust" since they began working with each other two months ago.
The DWTS pair is also fueling speculation by spending time with each other outside of show rehearsals.
Hannah, for example, brought the former So You Think You Can Dance contestant as her date to the 2019 CMA Awards last week, where the Alabama native stunned in a floor-length white gown that could pass for a wedding dress.
"He was great because my dress was, like... I think people think I'm joking when I say it was 50 pounds," Hannah told Us on Monday. "It was so long... It was a lot. So, he was awesome and very supportive, and we had a good time!"
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Alan has seen the best and worst of Hannah in recent weeks. The pair has experienced highs together, but Alan has also witnessed several emotional breakdowns.
For Monday night's performance show in particular, Hannah had to channel her painful and devastating breakup with The Bachelorette 15 winner Jed Wyatt, a Nashville-based musician who had lied to Hannah about the extent of his dating history leading up to the show.
Hannah had to open up to Alan about how Jed had betrayed her and broken her trust so he could choreograph a meaningful and symbolic contemporary dance for them to perform.
Not only did Jed have a girlfriend back home when he was filming The Bachelorette to promote his music career, but he had also promised the woman, Haley Stevens, they'd resume their romance once he returned home.
"It was a very vulnerable state for Hannah to talk about and tell me exactly what happened," Alan told the magazine.
"In order to put those emotions in the dance, we needed to open that can of worms and really talk about it in detail."