I wouldn't say she is a liar, I would do things to protect myself though.  Something I've done since contracting an STD is told them we can have sex once we've both been tested and I've seen your results and you've seen mine.  This isn't always 100% though, my doctor told me that it can take about two months for a blood test to show positive for herpes  (my first came back negative but I do have herpes)  if you have it and that unless you're having an outbreak its hard to determine whether or not you have it.  Sometimes people never have an outbreak, they're just carriers and it can take anywhere from 2-21 days for an outbreak to show up after being exposed to herpes.  If I were you I would simply go to my health department and ask for a blood test to see if I had it. I would strongly suggest doing the STD check and sharing results before having sex with partners, it makes everything less stressful.  Hope this helps.