"I support his decision either way," the 30-year-old tells PEOPLE. "Ultimately, football is a very physical sport and we only have one body. We have to take care of it."
"I know that with his decisions, he leads everything with his heart," Kostek says. "I totally respect his wishes to step out."
This is the second time Gronkowski has opted to leave the NFL behind and retire. In 2018 after a 9-year-stint with the New England Patriots, the future Hall of Famer called it quits.
But after sitting out one season, he returned to the sport as a Tampa Bay Buccaneer alongside his good friend and longtime quarterback Tom Brady. The duo enjoyed yet another Super Bowl win in 2021, and then Gronkowski called it on his career again this past June.
Mike Ehrmann/Getty Rob Gronkowski and Tom Brady
Although the three-time Super Bowl champ seems to have hung up his cleats for good, if he does decide to follow Brady's route and return to the game, his supermodel girlfriend would be supportive.
"I remember so many interviews that he did when he retired was, 'The only way I would come back is if my heart is fully in it,' " the Camille Kostek Collection designer adds. "He is a man of his word. His heart was fully in it. All it took was a season off and he came back. Look what him and the Buccaneers were able to do and win a Super Bowl the year that he came back. He played and hustled with his heart, so I am fully supportive of either decision."
But now, Kostek is happy to have her boyfriend of seven years home as they adjust to their new lifestyle together.
"There's definitely benefits of him retiring," the Sports Illustrated swimsuit model explains. "It means more time together and being able to take him on the road with me."
And just because the Wipe Out host isn't in the stands cheering for her man anymore, that doesn't mean she's leaving football behind.
The former NFL cheerleader has partnered with NBC Sports and dating app The League for SNF Match Ups, which will help people find love or friendship over their common passion of football at bars across the country.
"I am so excited," Kostek, who is hosting events this weekend in Tampa Bay for the Bucs and Kansas City Chiefs game, says. "Football is a huge part of my life and then it led me to [Gronkowski], so it bleeds into this whole partnership. It encourages football lovers everywhere to go spend Sunday night socializing with friends at sports bars and meeting up."