I have EXACTLY the same daughter, but mine is 5 now. All she likes to wear is skirts- and they HAVE to spin- or she wears her ballerina outfits or her princess dresses. And they can't have any loose strings or go passed a certain invisible point on her arm.
We let her pick out what she wants to wear- unless it's inappropriate- like for church or something- she cant wear her princess dresses to church. For those occasions, If she cant decide from the 3-4 choices that she has and she throws a fit I just tell her we are leaving soon and she needs to decide and then I walk away. She usually makes up her own mind in time for us to leave. If she hasn't made a decision after about 5 minutes then i go back in there and re-explain her choices and then walk away again.
If it's just a normal day and we only have park or store outings I let her decide what she wants to wear with no resistance from me. Even if it includes her wanting to wear the same thing she did yesterday- as long as it's not visibly dirty or smelly.
This has worked great for us as she used to be very inflexible on what she wanted to wear. but now that she feels she has some amount of control it has gotten a lot better, especially on church days and special occaisions where we are more involved in what she can and cannot wear.
I also suggest getting the book called "Raising Your Spirited Child" this had worked great for us in learning how to effectively help her to cooperate with us better by understanding how her little brain works. She's not like this in just clothing, but with almost everything in her realm, and I'm sure your little girl is just as veracious in other areas as well.
So, just take a deep breath and walk away. Plan ahead plenty of time before you to leave to take into account her tantrum- so she has enough time to decide and you aren't late for your appointments.