When I think better, we can't call her bad fairy because of who she is : fairy, faery, fae,fey,fay,faerie,elf,fair folk, kind one, beautiful one or however you want to be called, for most of their acts which we see as bad are completly normal from their perspective. There are few good ones, but most of them are neutral. How you treat them, they treat you. And kindness is very important in their culture. Even Unseelie court the ,,bad ones,,, who are more malicious intended than Seelie ,,good ones,,, consider it important. And this fairy surely belongs to them. Maybe she is has reversed roles with ,,good fairy,, for some other child. This theory is supported by multiple clues from original story: she backed off when she casted curse and princess pricked finger on some random deaf woman's spindle and her ,,sisters,, never showed concern for curse or called her bad. Actually, she casted curse because she didn't get gifts like others, so it is parent's fault for forgetting to call ancient, powerful more-than-godlike entity. Show them, fairies, and sorry for overly long comment, I got carried by picture's beauty but I think you could use wider palette choice.