The thing with Bachelor in Paradise promos is that they are often purposefully misleading. Even though the finale promo hints that Kendall Long returns to Paradise to break Joe Amabile and Serena Pitt up, it might actually turn out to be something completely different and way more innocent than that.
In the final moments of Tuesday's September 28 episode, viewers got a glimpse at what's to come during the ~dramatic~ three hour finale: Serena and Joe exchanging I love yous, and Joe standing on the proposal platform, perhaps ready to get down on one knee. But then Kendall shows up out of the blue. "She's absolutely trying to stop this right now," one of the other contestants said, while the promo flashed to a crying Serena.
But as we know, BIP promos are not too keen on depicting what's actually going happen. Take the promo about Ivan Hall and his tropical storm whereabouts. The scenes were edited to suggest that perhaps Ivan had snuck out of his room to meet up with Chelsea Vaughn, but we learned in the actual episode that he went to meet Alexa Caves. So even though Kendall appears to show up on the beach just in time to stop Joe from proposing to Serena, that's probably not how things will actually play out.
It's more likely that Kendall returns to the beach for some closure with Joe. Before she left, they had a tough conversation and Kendall admitted that she never stopped loving him. But Joe told her that he had moved on, and Kendall ultimately decided to leave the show. Perhaps, with some post-filming clarity, she realized that she'd also moved on, and she wanted to give Joe her blessing to be with Serena. Her return to the beach is edited to look malicious, but it could very well be her moving on.
Either way, Kendall has no regrets. On Instagram, she recently posted a long caption about the way she chooses to live her life. "I do what I feel is right. I say what I need to say. I don’t regret a single thing," she wrote. So whether she tries to break Joe and Serena up or she is there to get her closure and move on, Kendall seems to be happy with how everything played out. We'll just have to see how correct the promo is come October 5.