I'm going to tell my girlfriend about a private conversation in a group chat
Were you given permission to disclose this private discussion?
No, It's just that I am bored, I want to have some fun.
When you don't have the consent of someone else to reveal their conversation, it is not correct to share it with your gf. Honor the privacy of others and don't share information unless given the ok to do it.
What if people deserve being fucked over? Just because it's sensitive to them, doesn't mean it's my job to protect their feelings.
Whether you hurt their feelings or not is irrelevant, as it is a breach of trust when you disclose private conversations without permission. Keep what you hear to yourself unless given consent to speak of it.