To state the obvious:
1. Don't do it at all. Or
2. Learn a lot more about the disease than those in this thread offer. There is no way to be 100% safe but you can be pretty safe. I'll offer this as someone who had a ltr with a woman who had it:
a. Make sure you are both educated (but particularly her) about how the virus is spread. There are tons of resources out there. It can be spread obviously during an outbreak, when she is having symptoms but no outbreak, and there is evidence that it can be spread when symptoms are not present.
b. Make sure she can detect an outbreak. She needs to know where her outbreaks occur (harder for women sometimes than men). The virus doesn't just appear randomly around the body, but rather where the infection occurred. Don't have sex during an outbreak (ldo) or for a period after until there is complete healing.
As an example, it is entirely possible that she has it on her ass and nowhere else. Certainly then you can't get it from kissing her - or eating her pussy.
b. MORE IMPORTANTLY make sure she is educated so that she can detect the symptoms that precede or conicide with an outbreak. The virus can be "shed" when the symptoms are occurring.
c. Take precautions to reduce the chance of spreading without symptoms. Valtrex on a daily basis is the best way to reduce asymptomatic spreading as well as outbreaks and symptoms.
3. Use protection.
4. Get yourself tested. A lot of people are asymptomatic. I know a divorced friend who is that way and only got tested because of the nature of the divorce. Well, he knows now that he has it - but has no way of knowing when or where he got it (well of course he blames his ex). So now he has to disclose.
5. There is no reason that you can't do other stuff if she has an outbreak (which won't be much if she takes Valtrex).
6. There is no reason you can't do other stuff even if you don't want to risk getting the virus. I'm sure she'd give you a blow job!
Personally, if the chick is that hot and you really dig her, I would consider taking an educated risk. You might find that you get someone really awesome who others knee-jerked "no way" to. I think if you do all of the above, particularly the Valtrex, your risk is going to be very low. I had unprotected sex and oral sex for years with nothing happening but that was a risk I was willing to take.