Oh, she has her mind made up. She wants Mommy to do a show for her.
I am sure she is a sweet girl, but she is testing your resolve and your willingness to give in ter her. She is also probably at a stage where she is aftraid of making the wrong choice and missing out. And she just wants some control over herself. Totally normal.
However, it's your job to teach her patience in herself and you. So don't give into her. I am not saying be unreasonably strict. Yes, she is allowed to change her mind, but she can't have a tantrum if you aren't able to fix it just so.
At this age it is best to let her do for herself. Pack a box of acceptable snacks in the pantry or fridge, and let her get her own. But once she opens a package or the fruit is sliced, there is no going back. Make that clear. There is always a point of no return. Same with shoes, socks and underwear, let her pick whatever she wants, but again, no getting undressed after you get downstairs.
Pick your battles, let her make most decisions, but be firm about the decisions you have to make.
It will evolve and not always be quite like this. But you do probably have a good couple of years of this in one version or another. It isn't the mind-changing that is really the problem. It is her emotional reactions to not always getting her way. Let her change her mind as much as she wants. Don't let her throw a fit if she can't change her mind.
It will get better around 2. The terrible 2s really start around 16 months.