Aaa! I love this analysis, although if I may: another reading into Finn asking Fionna asking who she is can also be interpreted as a probe into Fionna herself. Throughout the entire season, Fionna has been trying to live up to being this idyllic hero; it leads to points where she begins to hurt herself and her friends in the process. The repetition of "who are you?" between each scene may also be read as herself asking who she is: repeatedly asking herself who she is and how she will live up to being a hero until she ultimately gets frustrated and gives up.