Have you two ever read the herpes handbook at www.westoverheights.com? It's free to read online or print out at home. It's a terrific resource for more reading.
Being on valtrex for years doesn't make your risk 0 but as mistakeguy already posted, it does reduce it by 1/2 of what it would be if you only avoided sex anytime your partner had obvious genital symptoms. Adding condoms helps with to decrease the risk but not a whole heck of a lot. You'll never get the risk down to 0.
It's totally up to you what precautions you want to use. Let your partner know that you are ok with the risk and she needs to understand that that. She is not a walking biohazzard by no means and is NOT contagious far more than she is contagious. Your risk is very low and obviously you are ok with that. If she isn't, discuss it more and even consider talking to a relationship counselor together to work through it so that this doesn't become an issue in your marriage to each other once that occurs. Herpes is such a small issue compared to all the other issues you'll have to deal with once you are married :)
grace
If you are not using protection but avoid sex during outbreaks and on valtrex the chance of you catching Herpes is about 2% per year. Pretty low compared to not being on antivirials. You can catch HSV if she is actively shedding the virus. But by taking valtrex that is a low occurance.
my partner who i met has been on Valtrex for a couple of years and the pass year we had unprotected sex. I went and got tested and my blood work came back negative. She is ok with the results and angry that she allowed me to convince her and not using condoms. I just can't explained why we did it without condoms only that I love her and we are getting marry.
So my question is if a person have been taken the Valtrex for years and have unprotected sex can that person be safe from not catching the infections because her blood is immune with the drug?