Not everything that happens requires a vet visit. Mice fight, especially male mice. Most times male mice will fight until one is dead. If it is just a scratch that is not constantly bleeding (which it appears to be from her emails she sends me), then as long as she cleans the wound and makes sure that it does not get bigger than he is fine. Vet visits are expensive and should not be used like air. I mean, would you take your child to the doctor every time they got a cut or a bruise? No, you wouldn't. The doctors would think you were crazy and need to calm down.
Now, if you have a valid reason or suspicion than yes, take your pet to the vet. But if they just get a scratch from a fight, talk more than others of their kind (-clears throat-), then there really is no need. You are just wasting your time and money and you are putting unnecessary stress on yourself and your pet. I am sure the pet does not like going to the vet, so why put them through that when there is nothing wrong in the first place?