As I read it, they are in an open relationship for now and spy wants to make enough money for the next step. Doc doesn't want her to get hurt so much, so she picked up this random guy to make her jealous. They seem to meet often, not just when Spy need treatment.
I guess Spy's work made it hard to get together for real because of her fear, so random guy is nothing more than an excuse.
It could be a total lie, too. We do not hear or see anything about him.
"If you'll let yourself be killed, I'll never be your girlfriend :<"