Himiko is obviously mentally unstable and has a very twisted perception of love and friendship. Proven when, despite wanting to kill Ochaco Uraraka and Tsuyu Asui, she attempted to befriend the two girls as they fought, affectionately calling the latter by her first name and describing the former as "lovely". When talking to Ochaco, she said that it was only natural to want to be like the one you love, to the point of literally becoming that person. Later she further explains and compares that like how "normal" people kiss the people they love as "normal", she sucks the blood of the people she loves as this is her "normal", further showing her twisted understanding of love, which thus justifies her carving up and butchering "guys who are tattered and reeking of blood", as they fit the description of her ideal lover. Himiko's interest isn't just superficial, as her questioning Izuku Midoriya about what his values and beliefs imply, showing that although twisted, she does indeed want to know more about the person she "loves".