Look at the cost of the classes and when the classes are held. Also the location of the studio. What type of dance do they offer? Some offer only ballet. Others offer jazz, tap, modern, etc. It won't matter now, but in a few years she may be interested in other areas of dance. All of that is basic stuff you've already thought of, I bet.
Of the studios you are still interested in, I'd go visit. See if the teachers are good with the kids. Some are sort of high-strung and unbending. Ask how many recitals they have each year and how many dances the kids will each be in. You usually have to buy the costumes, so it can be really expensive. And how many rehearsals do they have before the recital? Some have several and others only have one dress rehearsal.
You might want to talk to some other parents. What studio do they use? Do their daughters like it? Things like that can be really helpful.
Good luck making a choice. My daughter has been dancing for 10 years and she loves it.