I think it's pretty obvious, Meera, that you and SC have different views on relationship hierarchy. Probably why the friend's comment didn't make you blink while it bothered SC.
Perhaps you could have phrased your question in a way that was a little less harsh. The way that you said it gave the impression to me that you found SC's view to be just silly and and unreasonable. I don't know if that's what you meant but the way you said it, made me want to defend SC.
Also, I know assumptions are tricky but I'm not sure that you can judge better than SC about what her friend's assumptions may or may not have been. You have no context and no knowledge of the person. In Critical Race studies there's this term called a 'micro-aggression.'
Microaggression is the idea that specific interactions between those of different races, cultures, or genders can be interpreted as non-physical aggression. The term was first coined by American psychiatrist Chester M. Pierce and described as, "brief and commonplace daily verbal, behavioral, or environmental indignities, whether intentional or unintentional, that communicate hostile, derogatory, or negative racial slights and insults toward people of other races."
Microaggressions can take a number of different forms, for example, questioning the existence of racial-cultural issues, making stereotypic assumptions, and cultural insensitivity. Some other types of microaggressions that have been identified include Colorblindness (e.g., "I don't think of you as Black. You are just a normal person"), Denial of personal bias (e.g., "I'm not homophobic; I even have gay friends."), and Minimization of racial-cultural issues (e.g., "Just because you feel alone in this group doesn't mean that there's a racial issue involved."). "Colorblindness" in particular has been associated with higher levels of racism and lower levels of empathy.
To me, this comment was sort of an example of that. Something unintentional that reflects a cultural, structural, or something influence or idea in place that is inherently discriminatory.
If some one sees the relationship hierarchy as discriminating (not everyone does) then this could feel that way to them.