Hey Samthalo02, welcome to MalwareTips!
First things first, has anybody used the hard-drive since your girlfriend formatted it? Secondly, how was it formatted, was it a "Quick Format" or "Full Format"? If you don't know, then try to describe for me how the drive was formatted, for example, did your girlfriend right click on the drive and format it, or was it formatted from a recovery disk? etc.
Finally, if you could tell me the model of your drive then I can provide some more detailed assistance
The important thing is not to worry. In most cases we can quite easily recover 'most' of the lost pictures and videos etc.
Worst case scenario, if a secure wipe has been performed (this would have been performed with specialist software, so I'd be surprised if your girlfriend managed to do this), it may still be possible to recover something, although this would be a very specialist kind of operation and not the kind of thing I could advise you on how to do! You would have to send the drive away.
Until then, please don't use the hard-drive at all. Don't plug it into the dock or connect it to your computer or anything like that. The less use that hard-drive gets before we start the recovery process, the better chance of recovering your pictures and videos etc.