Pepper doesn't arrive on the island until hours after Steve and Tony do. Since the vampire debacle and Tony's subsequent reveal of what happens to her back home, she hasn't been very inclined to party or ever socialize excessively.
The fact that she still thinks Steve is angry with her over what happened in that alternate life has something to do with it, too. But Tony had spilled the beans and told her Steve apparently has similar beliefs about her, which had been hard to swallow. Evidently they need to talk, and though Pepper's never shied away from what must be done, seeking Steve out to do that has proven exceptionally difficult for some reason.
She keeps to the outer fringes of the party, watching the stars and the lanterns lit along the beach. She's actually thinking of going back to the mainland when she spies Steve by the bonfire. Sighing, she hugs her arms around herself and approaches. They can't keep avoid each other forever, can they?
"Steve," she says as she gets within earshot, giving a small smile, a bit uncertain. "Hi."