A Secret Relationship
When a person has just left a bad relationship, they often rely on friends and family to help them make the adjustment. Sympathy plays a large part in their interaction, and setting them up with dates could be part of what they all feel the person needs. It could work out well for someone ready for a relationship, but it might be a bit awkward if they have a secret relationship they are keeping from those who love them.
Being set up on a double date with a friend or relative and their partner could be a big surprise for the person who has yet to admit they are seeing someone, and the results could be hilarious if they are already dating that person. Both of them might have passed on telling their new partner about the date because they were going into it with no commitment, but their outlook might change when they are introduced by loved ones. They might not wish to admit they have been dating on their own, and transmitting this message to the other person could also signal their relationship has gone further than they believed.
Enjoying the date will give those who have matched them up the impression they have done well, so putting distance between each other might be a good idea. It will give their loved ones an opportunity to see that their interference is not needed, or it might give some breathing room to a couple not yet ready to admit their own relationship.
Fixing up couples is a tradition that has been around for centuries, but it is often awkward for those involved. When a person is recovering from a bad relationship, it can push them too far. A person secretly involved with someone else might have a good reason to keep their relationship from others, but the blind date could give them the opportunity to reveal it.