You need to talk to your partner about this. Find out if she's ever been tested to know her own status. Ask her how she feels about it all too. If she wants, you can utilize barrier protection when you perform oral sex
when you have obvious cold sores does go a long way but you can still potentially transmit the virus even when no obvious cold sores are present which is why making the decision together is best.
http://www.ashastd.org/herpes/herpes_learn_oralherpes.cfm is a good place to start reading more about cold sores.