Two and a half seems like a terribly young age to be dressing oneself! I've never heard such a thing. I wouldn't worry about a thing like that for at least another year.
Probably if you talk her through the routine, after a while she will want to do it herself and be a big girl. Because she is resisting right now, that probably means that she does not feel ready and it is probably intimidating for her - which, at 2 1/2, is completely understandable. The stress of pushing such things will cause for her, and how that stress can express itself more generally through a day (or interfering with sleep routines), probably won't be worth it to the family.
And here's something to get you through the frustrating moments, whatever shape they take. In Easy to Love, Difficult to Discipline, Becky Bailey points out that at such a young age, till about age 4, children are so absorbed by just figuring out all of the colors, shapes, sounds, simple concepts, interactions and the vast array of stuff they're being bombarded with that comprise daily life, that it can be hard to get them to focus on a specific task. We adults are so used to it that we forget that it's a whole lot to process. Their minds are already so full of information and everything is so new to them, so as frustrating as it can be, Bailey recommends using a lot of patience. It'll be easier on you, too!
Good luck and have fun with your little one!
L.