It could mean

1 You gave it to her.

2 She already had it.

3 She was mis diagnosed and doesn't have it.

4 You both had it all along.

5 You don't have it but she does.

6 You have it but you just don't experience outbreaks.

7 You didn't have it but now you do.

8 She had sex with 10 other guys since then and contracted it from one or more of them.

It's entirely possible that you don't have genital herpes. Johny has given you a bullet list of most of the possibilities. Here's another one. Suppose that you have ever had cold sores, even if you've never had symptoms and that you've performed oral sex on the girl. It's quite possible to have transmitted your oral type 1 virus to her genitals. About 1/3 of genital herpes cases are actually type 1. Do you recall ever having cold sores?

The only way you'll have a clue, not saying that it would be entirely conclusive, is to get some good type specific testing for both of you. When she was diagnosed was it by a type-specific culture? If it was by a visual "diagnosis" then it was really not a valid diagnosis as studies have shown that a visual diagnosis is wrong more than it is right.

As far as blood testing goes, it's a little early for you to get it and expect a conclusive result if it's negative, although a positive result can be trusted. The way these tests work is that they detect the antibodies that your body produces to fight off the virus. It takes some time for them to show up in detectable amounts. To get a conclusive negative, you should wait 12, or even better 16 weeks. The test you want is the Focus Labs HerpeSelect IgG for types 1&2. Don't let them to an IgM test as it's useless for this, and most, situations as it's not type-specific and only looks for transient early responder antibodies that fade away fairly quickly after the initial infection.

Good luck and let us know if we can help further. Keep us posted, too, so we know what you find out.