Thanks to Sister Grimm Erin for the headcanon that Lavender ships Harry/Hermione, a headcanon which I also used in my H/Hr story "It's No Secret." However, the two stories take place in separate universes; in this one, the story follows canon except for Lavender's death in the Battle of Hogwarts and the epilogue.
They meet in Flourish and Blotts, two years after the Battle. Ron wanders aimlessly around the shelves, waiting while Ginny makes her purchases. Lavender, with Celestina Warbeck's new memoirs in her hand, sees him as she glances over the edge of the mezzanine. Her first impulse is to run down the nearest aisle and hope he doesn't notice her before he leaves. But then she thinks: she can't run forever from all of her embarrassments. So she descends the stairs and nonchalantly approaches him.
"Hi, Ron," she says softly, making a conscious effort not to call him Ron-Ron, as she always used to do.
"Oh! Lavender," he says, surprised.
"Yes," she replies awkwardly. "Hello," she repeats, then blushes in embarrassment.
"So, erm... how are you?" Ron asks.
"I'm all right," she replies, though if she were being honest, her stomach has just become very upset. "You?"
"I'm... fine," he says lamely.
Lavender nods. "That's good," she murmurs. Then, to fill the silence, she asks a question she immediately regrets: "How's Hermione doing?"
Pain flashes over Ron's face. "She's fine, last I talked to her," he supplies. "But you know, we're not... together anymore."
"Oh, I see," Lavender replies, though she doesn't really.
"She and Harry are..." Ron trails off.
"That's so cute!" Lavender blurts out before she can stop herself. Ron frowns. "I mean, I'm very sorry for you," she hastily adds, "and for Ginny too —"
"Oh, Ginny's the one who broke it off," Ron says. "She said they weren't going anywhere."
Lavender nods sympathetically. She is genuinely sorry for the siblings, even though she's pleased to learn that Harry and Hermione have seen in each other what she saw several years ago. And she must admit a certain pleasure in hearing that the girl who broke up her first relationship, however unintentionally, has now left the boy who left her.
"Well. It's been nice talking to you, Ron," she lies as she extends her hand, somewhat formally.
"Yeah, nice talking to you, too," he replies. Then, as he shakes her hand: "Want to talk again?" His own words seem foreign, disembodied. Why did I say that? he wonders.
For reasons she doesn't understand, Lavender's heart leaps. And though she wonders if it's really a good idea, she has learned to let her heart rule her brain — even, perhaps, when it comes to Ron.
"Yes," she replies quietly. "Thursday, perhaps? At the ice cream shop?"
Ron considers it and realizes he can't very well back out of his own suggestion. Besides, he reasons, it will be nice to talk to another classmate, even if it is his ex-girlfriend... won't it?
"All right," he says. "I'll see you then."
As Lavender walks to the registers, she wonders why she feels so happy. She tries to suppress it, knowing that the last time she was happy to see Ron, it ended with his breaking her heart.