It is rude to snoop through other people's private messages.
Dave is dating a partner who has a friend who he is feeling jealous over.
Dave wants to see if there's anything going on between them.
Dave finds a way to casually ask his partner about the nature of their relationship.
Dave takes his partner's phone and starts looking through her messages.
Dave's partner feels bad for the misunderstanding and reassures him that it's just a friend.
Dave's partner catches him snooping and is upset about his lack of trust.