Sneaky joke from Toby Fox is that althought "fawn" commonly refers to a young deer or a light yellow-ish brown color, like Noelle's color palette, the term is also connected to "fawning", which is a trauma/fear response.
It's a common sign for people with this trauma response to stifle their opinions or preferences out of fear, which is something Noelle tends to do.
Fawning is also characterized by compulsive caretaking. People with the fawn response will attempt to de-escalate conflicts, even when it doesn't involve them.
They will fix or rescue other people from their problems, something Noelle does to a certain degree. (Even the times when it could be easily read as Noelle being overly obsequious to Susie, because of her crush.)
Of course, this behavior may come across as being overtly cooperative, agreeable, or selfless. But in reality, it's compulsive; in other words, the individual is aware of these behaviors, but they are unable to stop it. (Which can lead to resentment.)
Another common sign is being unable to say "no" to others. It's distinguishable from people-pleasing tendencies, because then it would imply some degree of deliberation, unlike the fawn response which is an unconscious process done in order to keep us 'safe'.
This could explain why Noelle is overly-accomodating to Queen's wishes, because she just cannot refuse.
This response is born from environments where enforcing boundaries, expressing anger, or wanting to get your needs met led to punishment or withdrawal.
This could explain why Noelle feels comfortable, or rather, safe, saying "no" to Kris and Rudy. Kris can be very respectful of someone's boundaries, and Rudy only wants what's best for Noelle and isn't harsh on her, unlike Carol. They are people she isn't afraid.
This could be why even after what happened with Queen at the end of Chapter 2, Noelle still falls short in trying to be more assertive at times. The fawn response is a deeply rehearsed pattern that can't be unwinded easily or inmediately.