In a new interview with PEOPLE, Randolph, 26, opens up about her relationship with Reinhardt, saying their bond started long before they became romantically involved.
"I love everything about him. But I love the fact that we were friends for like six, five years, I think, before we started dating. I think that really helped make us really strong," Randolph tells PEOPLE while discussing her new collection with Lilias Active. "I think it was like six years ago now probably, we had a little thing but nothing ever happened. It was kind of that we were really young and then we just became friends. And that was it for years. We'd hang out with each other's siblings and families and stuff."
PEOPLE confirmed that Randolph and Reinhardt were dating in May after months of speculation.
"Last year, we re-connected and it was game over from there," she says.
Compared to her past relationships, Randolph says the relationship "feels so much more natural and better" with Reinhardt.
"He's honestly my best friend, which I think is such a key thing to have in a relationship. ... I feel like I haven't really had [that] before," she continues. "I feel like we get each other on a different level, especially being friends for so long before. It just made it really natural and easy."
Randolph rose to fame while competing on season 23 of The Bachelor, where she met ex Colton Underwood.
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Randolph says she's been able to learn "so many things" from her time on The Bachelor. The most important lesson: "To just not stress too much about what people are thinking about you or what people are going to say."
"I have a tendency to definitely be a people pleaser and I think that has completely gone away just because you almost can't be in this world," she continues. "I mean, I definitely still have a tendency. As far as the public eye and stuff, people can be really hard on you. So just having a thick skin and being true to yourself and trying not to pay attention to what people are saying too. Because if you read everything people are saying about you, it can really mess with you."
That "life lesson" was also one of the reasons she kept the start of her relationship with Reinhart private. "I didn't want to bring that on other people while all the craziness was going on," she explains.
According to the former Bachelor contestant, the couple wanted to keep their romance on the down-low because they "didn't feel like dealing with the public eye."
"I think we're both just pretty private people in general," says Randolph. "When I was thrust into this spotlight of some sort, it definitely was an adjustment because I wasn't used to it. I'm a pretty private person, so I think it just kind of is we'll share things if we want to. It was important to kind of keep quiet and kind of figure out what we wanted and do our own thing at first."
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Being a part of The Bachelor has also provided Randolph with many unique opportunities post-show, including her own collection with Lilias Active. As a longtime fan of the activewear brand, Randolph believes launching a line of her own with them is a "natural progression."
Randolph's collection is more loungewear-focused, featuring neutral and simple pieces. "You can kind of wear them with anything, but they do come in a few fun colors," she says, adding that she wanted the line "to be really versatile."
As for her favorite item? "I love sweatshirts," she says.
"The sweatshirts are super comfy, kind of oversized. I hate it when sweatshirts kind of, like, bunch at the bottom and ours don't do that. They fit really well," she continues. "I also really like the tops. The tops are really cool because you could wear them with jeans or out or make a full outfit with it but also have a built-in bra."
Randolph's new collection with Lilias Active launches on Thursday.