Well, some of this need to have things just so is normal for a kid her age. But if it's taking up tons of time or causing huge arguments you could gradually get her used to things being not so tight.

First figure out what would be an easy thing for her to do -- for instance, leave her hair not-so-tight for five minutes. You could ask her if she could do that if she really, really tried. If that's too long, ask her if one minute is too long. Say, "I'm not going to make you do it, but if you had to, could you? I just want to understand." Use your mom skills to find out what she'd be willing to do if she had a reward. Then offer her the reward for doing the easy thing -- even if it's leaving her hair in a loose ponytail for 30 seconds. Praise her a TON for that. Don't imply that it's going to get a lot harder. Just praise her, and then the next day, try again. Say, "I'll make your hair as tight as you want after, but can you leave it in a loose ponytail for a whole minute today? And you'll get... XYZ."

So, go slow, don't punish, don't yell, see what she can take in little increments, and reward her; eventually she'll learn to tolerate things being loose. Make it into a game if you can.

Hope this helps.