the bones of it would be that they've had a messy fwb situation going on for however long, she's terrified of commitment but gets her panties in a major bunch if he flirts with girls or goes on dates whatever. basically she has hearteyes like a mother but it freaks her out. everything is totally open for brainstorming and discussion just dw something that flips between those cute cuddled moments and stupid arguments over the dumbest shit imaginable.