The act of letting go of Elsa portray her strong personality. She was not afraid to show who she really is. This decision she has made of course, follows a big responsibilities to take charge however, she does try to embrace whatever it would be which in time will benefit the kingdom or the place she has been.
Elsa portrays a woman who, in the end, was not afraid to accept and embrace who she was despite what others may think. She also didn't see the need to ask or run to a man for help, which in my opinion is a very strong characteristic of an independent woman.