I'm going to tell my friend his grandmother was snooping for money
Why would you say something about your friend's grandmother?
Because I'm jealous of the relationship they have together.
Gossip has great destructive powers, and you should not use it against people you care about. People use gossip for their own selfish interests at the expense of others.
It's cool that I get to ruin my friend's relationship.
You are very low to ruin someone's relationship with their grandmother. How would you feel if someone ruined a relationship for you?