Helloooo! So you can see all of my characters here, but in the meantime, here's mine that I figure will know Gwyn outside of the obvious that is Nick.
This journal is Eve Ritter! She's originally from NYC, but moved down to Dunhaven in 2015 to work for her step-sister, who owns Stella's. Eve runs the food truck, which can be seen around Dunhaven, but also spends time in the DC area. She also works at part-time Roll of the Die, so she can be part of D&D nights and get an employee discount. That being said, she's Gwyn's age and they're both redheads, so I feel like they'd be kindred spirits and would get along really well! So they could be friends? Gwyn could have stopped at the food truck at some point and they just got to chatting and history was made?
I also have Calla Puri (~petals), who would potentially know Gwyn through Vee and Jahan. There's also the canon connection, which could maybe come into play someday if we get ourselves a Harry and all that!
Rowena Hyland (~ofhyrule) is two years younger than Gwyn and went to Athena instead of the public school, but her family is pretty known in town as they've been around for ages, own the vineyard on the outskirts, and have lots o' money. They also are known around town as the family that lost their youngest, Clara, who was kidnapped when Rowena was eight. But yes, there's potential for them to know each other; despite being born into a wealthy family, Rowena is really down to earth and could use some friends. XD They could have known each other in childhood, maybe before Gwyn got ~cool~?
SO YEAH that's what I've got for now. If you see any connections I'd miss, don't hesitate to shout.