We were on the final mission. One player wants to use her good luck charm. She has to choose between two Snow Trial cards. Our other teammate asked her to please remove the Snow trial with the Shells. He didn't give an explanation. Just that it would be nice if that card Trial card were removed. Is valid or is that considered cheating?
To me, that sort of help is against the rules. The rules say:
Some information in The Grizzled can’t be shared among players. The contents of the cards in each player’s hand cannot be re- vealed.
In your situation, the help that was given was based on knowledge threat the player had of their own hand, knowledge which cannot be shared. Although they didn't specifically say what card was in their hand, the information given strongly implied information about their hand.
But discussing the options based only on what's visible to all players should be fine. For example, pointing out that there's already 2 rain cards, but only 1 night card, so it's less important to get rid of the night card. The rules don't address this sort of thing directly, so it would fall into the same category as allowing any sort of strategy discussion while playing. Some groups may choose to not allow any discussion at all; but rulebooks don't generally cover the scope of general discussion like that.