patience or control?

At two and a half years old my daughter and I have a lot of issues.

Let me start by saying that I believe I truly have a wonderful daughter. She is overall polite, creative, smart and energetic. She is sweet and loving to her sister and Polly.

BUT she is also headstrong, stubborn and very independent. She moves at her own pace.

Right now I am struggling with how to deal with her independence at two and a half years old. She wants to do everything herself. And for a long time I have allowed her some flexibility to do things for herself. I probably gave her too much freedom too young. This is coming back to bite me in the ass. She takes FOREVER to do certain thing that she insists on doing herself and won't I don't let her do it herself a tantrum is sure to happen.

For example, she wants to climb out of the car herself. No big deal right? She is a big girl and should be able to jump down out of the car herself. However, when I let her do it herself to prevent the crying she inevitably climbs into the middle, down underneath Avery's seat or all the way up to the front. This is followed by several commands, counting, yelling and threats of spankings to get her to come out of the door.

SO in that situation should I have more patience or more control? Should I have the patience to just let her explore and know that eventually she will come out of the car like she is suppose to? What's the big deal anyway, it takes all of about 1 minute for her to do it herself? Or should I have more control and get her out of the car myself and then punish her when she reacts poorly to not getting her way?

We have a similar situation to her wanting to put on her own shoes, putting her underwear/clothes back on after going potty, drinking out of a big girl cup, and many others. I think that some of these are skills that she should be working on and be learning how to do on her own. But how do I know when I need more patience and when I need more control?

Any thoughts?