Alicia's actually curvy tho. She considers herself to look like a curvy American Girl doll. Hair and complexions and height are definitely different tho
If he gives her the nickname it doesn't inherently have to fit the way that she makes the first move but rather how he sees her. If he considers her cute, or delicate despite that not being the main way she shows herself it could be used to show his character (if it fits ofc) or layers to her personality.
Personally I think a lot, though certainly not all, of tough girls still want to be considered feminine and delicate in context even though they still don't want to be underestimated (maybe just because this is my POV myself lol) so dichotomies like this are something I like to show a lot.
I have a lot of women who are borderline (or actual) super heroes who still want to be carried by their husbands/boyfriends when they're just dead exhausted. The female lead of my two new novels are both pretty no nonsense, and also pretty tall girls, but they don't want that to make people think they are made of stone. Might not suit your character but it's a possibility.
It could also not be as cute as it is just suiting her personality or looks. Say, since you mentioned her being a ginger, if the hair is red enough he might call her something like "Ember." Or he could call her something like "Sprinkles" or "Cinnamon" because of the freckles