My wrist is 15cm, Small juc 16, Loves both 17. Mine are all on the 'loose fitting" n not snug,. It only works better for those who have a slightly snug fit. My friend have 16cm love n her wrist is same size as me 15cm and her stack is so much better, less movement. I could honestly do 16 but I prefer loose when stacking.
Mine are loose fit. My wrist is 13, I wear 16 Loves and a 15 Juc, and could go down in size for a snug fit; our fits sound exact same. Sounds like maybe you aren't loving your small, if you can sell it for something you love, you should! If you don't need to free up funds, I'd keep it, but again I love the small Loves!