Girls are fond of accessories such as purses or change bags. Even if they have many, they would still be delighted to get one more. Buy the Disney themed purses or, if you find them expensive, you can go with the small fancy purses or change purses. You can replace these bags for the favor bags and fill them with candies, inexpensive jewelry, feather, stickers, bubble mix, etc.
Parents always love things that their kids can use for learning. The bubble mix, the wand, the cookies are always being the favorites of kids but they need a push to learn something new. Apart from giving them a lot of fun time to relax and enjoy, send them home with a coloring book and a set of crayons. A story book will also be a good option to include in the party bags. These favors will not cost you much but will surely get you a lot of appreciation from the parents.
A pack of make-up accessories
Girls are fond of anything that will help them to look beautiful. While parents do not encourage the little girls to do a lot of makeup on a daily basis, they will not mind if you give them the accessories. Give them a good quality hairbrush to manage their tresses and a fancy looking gem-studded hand mirror to see how beautiful they look when they smile. Include a pack of face wipes in your favor bags so that the girls can clean their faces whenever they want. This bag would be something that will pamper the little ones and make them feel like the real princess.
Buy the Disney themed personal diaries for the treat bag and encourage the little girls to start practicing the habit of writing dairies. This will not only help them to spend some time with themselves but also boost their writing skills.
These are just a few options. The princess theme is so famous that you can easily get any Pretty Princess Party Supplies that you want.