Most marshmellows come in a packet that has two colours: white and pink. So my suggestion for the cutie mark would simply be two marshmellows, one of each colour, sort of overlapping. Kind of like this:
If you loved the amazing cutie mark cupcake toppers from , you are in luck!! We have Lynlee of here giving us step by step instructions on making your own cutie mark toppers!
Join The Quest That Everypony Must Take: To Find Their Own Cutie Mark!In Equestria, being true to yourself is the key to earning your cutie mark. But staying true to yourself is just as important! Join Twilight Sparkle, Apple Jack, Pinkie Pie, Rarity, Fluttershy and Rainbow Dash — as well as everyone's favorite Cutie Mark Crusaders, Scootaloo, Sweetie Belle and Apple Bloom — as they journey to find their own Cutie Marks, take on the spirit of chaos and disharmony and visit a village where… everypony has given up their Cutie Marks?! It's all here in Cutie Mark Quests!