Agh, it's been forever since I've written a short story. We unfortunately only do research papers in English this year... Except for the occasional written assignment that's usually about analyzing the meaning of something we read in class.
Let's see... Well, your teacher seems to want a story that's realistic fiction and you already have the general idea of the characters talking to each other about something. What you're stuck on is what they're talking about and how they encounter each other.
As for what they're talking about, perhaps a recent event in one or both of their lives? As for the event, I'd base it on something currently happening in your life or a memorable event from your past. Write What You Know
. Then, use said event to help determine where and how the encounter is initiated. For example, if the event is more serious, such as the death of a family member, maybe one character is visiting the other to try to comfort them. Or, say, there's some exciting event about to take place, and the two are discussing it at the local café. Then depending on how long the conversation is and how long the story has to be, you can follow up with focusing on what happens afterwards, whatever that may be.
Does that help?
“DAMMIT WHEN I HEAR 'SPACE CQC' ALL I CAN THINK OF IS BIG BOSS WITH A FISHBOWL ON HIS HEAD, STRANGLING AN ASTRONAUT OUTSIDE THE ISS."