I am a lesbian. My new girlfriend has a cold sore on her mouth. I understand that I shouldn't kiss her/let her go down on me. My question is: do i risk getting herpes if i perform oral sex on *her*.  

No.  If she only has oral herpes, it is safe for you to perform oral sex on her without risk. Please know that she can transmit virus to you even when she has no symptoms through asymptomatic viral shedding.  About 75% of people infected with HSV 1 do not recognize cold sores.  Have you ever been tested to know if you also have HSV 1?

Terri
---

I have not been tested. But I'm 46 and have never had an outbreak. And i was in a monogamous 20 year relationship with a woman until recently. But, I see now that I should be tested because if I already have it, it don't need to freak out.

I agree that is you test positive for HSV 1, your risk of acquiring HSV 1 from your partner is very low indeed.  The catch here is that the IGG test misses 30% of HSV 1 infections, compared to the herpes western blot.  So if you test positive on the IgG test, that's a clear answer but if negative, not quite so clear. 
I think you are a bit unclear about how herpes is transmitted.  It's not as easy as you think.  If she has no cold sore present I would not worry at all about you getting it from her hand nor should you worry about sleeping next to her and touching her pillow.  Those are not ways to transmit herpes.  I am happy to answer further questions about transmission that you might have OK? 

Terri
---

She has an active cold sore. (She is taking medication for it and putting Abreva on it. ) I'm concerned with fluid from the sore getting on the pillow cases/towels etc.

I understand that she has active cold sore right now but herpes it not transmitted via virus getting on something like a pillow case and then getting into you.  It requires direct contact.  Virus left on a pillow will die very quickly as it is dry, cool and there are not human cells in which to live and reproduce.  If she is taking medication for it as well as applying something topically, I would guess that there is very little living virus around anyway.  Sometimes, what takes the time with a cold sore, is the skin healing, not the virus going away.

Terri
---