How many hours did it take to add your labels to all those cartoon invoices? I'd worry the time spent merging systems outweighs the kindness of keeping hers intact.
Haha, I feel you on that 'how are you supposed to find anything' part. My niece once color-coded my invoices with stickers based on her favorite cartoons. I was lost for a week. What I did was keep her system for fun but add my own labels in the file names, like 'fun_project_emoji' alongside the real client name. That way, I could search properly but still appreciate her work. It took a bit of time, but now I can find stuff and she feels helpful.
Actually, mixing systems sounds like a recipe for more confusion. Having two labels for everything would just mean double the places to check for files. Sometimes a clean break is kinder to everyone involved.