She flew in, from over the horizon. "It's not really star-gazing without any stars," she told him as she landed.
"There's that star over there," he said, pointing toward the northern horizon. He was near the south pole, so that was always visible.
"Yeah, but you're not looking that way," she pointed out. "You're just staring into the blackness of space."
"Would you rather I stare into the blackness of your heart?"
She stuck her tongue out at him, then laid down on the dying grass next to him and took his hand in hers. "We're the only two who saw it through," she said to him. "We're at the heat-death of the universe, with our man-made planet orbiting a man-made sun with all the matter left in the universe, and you still have to crack your cruel jokes."
"Well, there's not much else to do," he pointed out.
"There's always each other," she said with a grin.
"You know, I consider puns the cruelest joke of them all."
"I'm literally the last woman alive in the universe," she reminded him. "I've also got the better part of ten to the seventh Earth years to work on this," she said, looking at their sun, their timer. She stood up again, preparing to fly away. "At least I'm not bored: I've got a really good puzzle to solve," and with that, she was off over the horizon again.