Does it count as cuckoldry if the observer wasn't in a relationship with either of the participants? Trying to figure out whether or not this is a 'poorly-disguised author's fetish' thing, or just a blatant author's fetish thing.
Before the cuck-inflation, wasn’t that just voyeurism?
One who has a monogamous relationship who likes to voyeur the partner having sex with others and gets sexual gratification of it. Here the protagonist has no sexual or romantic relationship with either of her close friends, so the answer is no.
Like Thomasina said, this is voyeurism, which can be someone's fetish as well.