Natasha and Bruce
Yes, Bruce was with Betty, and he was happier than he'd been in years. That didn't mean he wanted to push his friends away. Yes, he was aware there was something there with Natasha. Something they'd been close to and lost. He also thought there were things she wasn't telling him, still. But they were in a new place, surrounded by people they'd long thought fictional. This wasn't the time to push away any friends, and he still very much considered Natasha Romamoff a friend.
Taking a drink from the bar, he made his way to her side, taking a seat next to her in the sand. At least he wasn't the Avenger wearing the grass skirt. "We really should stop him," he said casually, nodding towards Tony.