I don't consider her one. I think some people consider her an antagonist because she made a lot of mistakes during the movie. However, she was breaking from the stress and couldn't control her emotions. She wanted to help Anna and Arendelle, but she didn't really understand her powers and I personally think she was afraid of making things worse. Disney was originally going to make her a villain, but I'm glad they didn't because just because she made some mistakes, she had a good heart and meant well. Whether or not Elsa is considered an antagonist is based on opinion. I consider her a protagonist :)
Antagonist = the character that opposes the protagonist.
Deuteragonist = the second character that the media focuses on (the protagonist obviously being the first).
I heard that Elsa was, in early preproduction, considered to be the villain/antagonist of the movie, but a lot can change in movie production and in her case her role changed a lot!
Elsa is not an antagonist. She isn't evil. She does not want to kill anyone, take over the world, etc. (which is pretty much the motive of every antagonist I've ever seen). She is more of a protagonist. In truth, Anna and Elsa are each other's foils.
Foil: a character created to demonstrate the qualities of the hero through comparison and contrast
posted over a year ago
Actually Elsa is the deuteragonist, not quite the protagonist.