At least SOMEONE in this manga has their head on straight.
Really? I think it's the opposite
Obv his friend conveniently checks all the right parts in his explanation because things have to progress, but I do believe it's the opposite of what he says: in reality, people say normal things in the face of a person for whatever reason (avoid drama / fighting, keeping up a facade, and such) and their real thoughts leak out when with others, because they don't need to keep up a mask anymore.
So...no, MC has all the rights to believe that her real thoughts are the ones shared with her friends.
Also because if you are truly are a friend -or more- you don't double down and belittle the other person in front of others, instead you defend them.
More so because it wasn't just a discussion about liking him or not, they were straight up spreading bad lies about him that put him in a bad light.
MC have all the rights to be hurt