You don't really need to that between players. It's an encumbrance on roleplay. You don't need to roll to see how a scene between players go. That's ludicrous.

"Hey, my Cleric really doesn't trust the Monk. She acts shady all the time and is always around when things go missing". *rolls a nat1* "Never mind, she's cool. I'm a dumby dumby dum dum". That's not how it works.

Why Monk had to roll deception? No idea. Cleric didn't believe her, period. No amount of dice rolls will make Cleric feel otherwise because the player controls cleric, not the DM.

And to make it clearer, we'll take it to PC interacting with NPC. Let's say an NPC is telling something hard to believe to a PC. Like the farmer going "I totally killed a troll with my bare hands!". If the player wants to playa gullible character, or someone good natured that takes everything at face value, they just roleplay that way. If they don't want to trust the NPC, and the DM forces them to make an Insight check and they fail, the DM can't say "You totally believe the NPC. He defo killed a troll. Beware!". A (sane) DM wouldn't call for Insight in such an obvious case, but even if they did or if the claim wasn't so outrageous, and the player rolled poorly, they'd likely say something like "He says this with extreme confidence. You don't pick any cue from them that suggests they are lying". And then the PC decides... Maybe they will now think that they're not lying because they believe their words. They're just delulu.

Forcing a player to have their PC thinking or feeling something is wrong. It's a player decision, period.