"I would say that there's a very strong possibility they'll get engaged when he comes home."
After seeing them together at Usain's restaurant in Jamaica, Christine also said she thought Kasi was "the one" girl for Usain.
"They like the same music, the same food and doing the same things together and it makes sense for them to get together," she told The Sun.
She also said Usain has expressed interest in starting a family on day, and that Kasi was one of few women he had been in a "serious"relationship with for a long time.
"I've talked to Usain about starting a family and he says he wants to, and I'm sure he will now he's achieved so much," she said.
"Usain has had a few girlfriends, but not many - but no one ever as serious as Kasi and I'm sure he'll be settling down with her before long.
"I think she's the one."
Bolt's Jamaican girlfriend sent the internet into a frenzy after she began posting messages of support to him during the Olympic Games on her social media accounts.
Bolt recently referred to them as "President and First Lady" in a photo he posted on Instagram.
Bennett is prolific on social media with her support for Bolt and her passion for fashion and selfies she shares with more than 30,000 of her followers on her Instagram account.
After Bolt convincingly won his triple-triple gold medal haul, leading Jamaica to the gold medal in the men's 4x100m relay, Bennett posted on her Instagram: "Respect the legend".
Just days ago, she posted that Bolt's success story at the Rio Olympics had already written. "Time to publish", she wrote on Instagram.
On Twitter, she also described him affectionately as "My Boss" and "My babbbbbbbbbbbyyyyyyyyyyy!!!".
