I have two in the same tank, but they are still juvinilles and don't know what sex they are yet. So a scrap might come yet. I know that you can't keep two males together but two females or male and female might get on okay. trial and error me thinks. good luck.:2thumb:
If you were to you would be best of with a female - to avoid breeding and unwanted eggs. Plus males tend to pester the females.
You would also have to quarentine the new beardie for a minimum of 3 months (usually recommended) to ensure she was eating, pooing etc ok incase she was carrying anything which could pass on to your other dragon.
You would also be advised to keep a spare set-up incase they dont get along or at any point one turned on the other.