N.K.
I don't have a specific dance studio to recommend but I can definitely provide lots of tips on choosing one. I'm a former dancer & dance teacher myself!
~ Look for a studio that has levels ranging from 3 year olds (or even 2 year olds) on up through teenagers or even moms classes. If it is just a studio with simply little kids and that's it then there obviously isn't much room for her to "grow" sort-a-speak.
~ Next I would recommend finding a studio that does competitions and is "well known". NO your daughter wont be doing competitions this young and she may never ...however studios that do competitions are usually more reputable and have the opportunities for your daughter to thrive if she so chose (down the road).
~ Last but definitely not least... go to some of the shows that the studio offers. For one it will allow your daughter to see it and create an interest, and for two you can check out whether the older girls are a little to PG-13 or even R rated or if they can keep the shows and the girls dancing at a PG level. No 4 year old, 10 year old, or even 18 year old needs to be dancing like a you know what! I'm not sure about your personal thoughts but I'm guessing most people don't want to think about their daughters being too over the top.
Growing up I was at a very conservative studio... yes we did have some steps that involved shaking our hips and what not or maybe sometimes our costumes were a little skimpy but never to the point of being anything more then a family show.
You cannot start in the middle of the year so you will probably have to wait until summer camps start which will be in June OR you can wait until next season which starts in August and runs through May. This should give you plenty of time to choose a few and to go to their shows to get a feel for things.
Most of the things I listed are really only relivent if your daughter sticks with it long term but it never hurts to plan ahead just in case. I hope this helps! If you have any other questions feel free to ask!!!