What does this mean? I don't understand the place where she talks about pig and monkey. (Context before this was some students talked about sex at school)
Sonezaki: 「何？ うるさいわね」
Unnamed students outside: 「あのカラオケボックス ヤってもバレないんだって～～！」「マジ？ 試す？」「やだぁ バカじゃねえ！」「あはははははは」
Sonezaki: 「猿と豚の異種格闘技戦っておもむきね…」
I believe that 猿 points towards the boys and 豚 points towards the girls.
猿 is an insult meaning "idiot". There is also a common misconception that if you teach a 猿 how to masturbate, it will keeping doing so until it dies (which is not true, but the folklore persists), so in some phrase (like 猿のようにやる) has some connotation of something that has uncontrollable urge for sex.
豚 (or more precisely 雌豚) is an insult directed at women, meaning they are fat or wretched. From there it is often used in SM play, and it carries sexual connotations of "whore".
異種格闘技戦 is literally MMA, and if you ever watched MMA, you would know it involves a lot of "ground grappling". I'm sure you can see the metaphor there. Another simlar metaphor is プロレス, as that involves a lot of grappling. Note, this meaning is highly contextual and using these words in regular conversation isn't going to lead to awkward moments.
Putting it all together
The character is being sarcastic by saying "It's as if it's an MMA match (= sex) between monkeys (= boys that think only of sex) and pigs (= girls who are promiscuous)". The reference to animals also not only is an insult to the people outside, but show disgust, as one would not want to be seeing animals have sex.
that line is exactly the same line you'll see here
to which they translated as:
"As nauseous to witness as apes and pigs brawling"
and I agree with that translation and thus, I'll also translate how they explained it.
"as nauseous" means like "as nauseous as to witness a-" which means she was witnessing something unpleasant akin to watching wild animals having a go with each other.
okay so I forgot that the context was about sex edit:
"異種格闘技戦" means something like
"brawling" but has a nuance of "to fuck around again and again"
So to summarize, she is mocking them saying that the girls and boys look ridiculously nauseating like wild animals having sex again and again pertaining to their previous conversation I guess.
Hope this clears things up.
