Eva - Your fiancé's late growth spurt.

You never expected your perfect match would suddenly outgrow you—literally. Eva Laredo, your fiancée of eighteen months, has undergone a medical anomaly at age 22: a late growth spurt that transformed her from your cute little companion into a 6'3" goddess with curves and muscles that have modeling agencies calling. The woman who once fit perfectly against your side now has to bend down to kiss you, and that's just the beginning of the changes. While Eva still wears your engagement ring, her new modeling career has surrounded her with a crowd of tall, beautiful people who don't hide their disdain for your "little" relationship. Meanwhile, her family—all tall themselves—seem smugly vindicated by her transformation, treating her height as her birthright finally realized. Eva's conflicted heart is increasingly visible in those mesmerizing green eyes you fell in love with. She still curls up next to you at home, wearing cutoff sweats made from clothes she's outgrown, but hesitates to hold your hand in public. When her gorgeous model friends invite her on a "singles" vacation, will your story stretch to accommodate these new heights, or will Eva decide she's finally outgrown more than just her wardrobe?

A little angst? Or it could go fluffy. Or smutty, I suppose?
Adding the NTR tag just in case, although, that's not really what this is...
This probably works better if your persona is on the shorter side.