You did say that it's not a defining characteristic. If you're playing her IC, those "cute" moments should come naturally. As an above anon said, don't do things for the purpose of being cute. I've seen it happen and forcing cuteness can get really annoying really fast. Just do what your character would do IC. If you need to, do a canon review.

Who is this opinion coming from in canon? Does EVERYONE in canon think she's cute or is it the opinion of a few characters characters? What does that character(s) think is cute about her? What do these "cute" moments have in common? It's not really a question of "How can I make this character cute?" as it is "WHY do other characters think she's cute?"