Mail received displaying sending last name twice - why?

Here's a strange issue. I recently setup a new user on our domain for email, which is hosted by Google Apps. The new person (we'll call person 1) is using OSX 10.8.3, latest mail, etc... their mail settings on Apple Mail appear to be set correctly and I had this person send a message to myself and got it fine, formatted correctly.

However, another person (we'll call person 2) in the same domain will get messages from this same person (person 1) and the name which is put next to their email address displays their last name twice. As an example, here's how we typically setup email addesses:

first.last@ourdomain.com

This person (person 1) would send a message and only certain receiving people (person 2 and others) would get an email with the address formatted as such:

"last last" first.last@ourdomain.com.

Could it be the person getting mail (person 2) in this way has not enterted this new person (person 1) as a contact in their address book? I'm also being told that the same person (person 2) who is getting this strange formatted email when they try to create a new message to this person (person 1) and start to enter their name, the mail cache as remembered the same formatting as above, where the last name is repeated twice with no first name.

Hopefully this is not too confusing. I haven't been able to confirm person 2's address book to see if that's what's going on, but I suspect so.

Any idea what's going on here?