Have you had a test? You should have one. About half the adult population has hsv1 and doesn't know it, since 90% will never get symptoms.
If you have it already, you don't need to worry about anything. You can't get what you already have.
Actually, oral hsv1 sheds more than that. I'm not sure where you got that 10% figure.
HSV 2 genital 15-30% of days evaluated
HSV 1 genital 3-5% of days evaluated
HSV 1 oral 25% of days evaluated
HSV 2 oral 1% of days evaluated
There are no studies on transmission rates for hsv1 like there are for hsv2, so I can't tell you that.
I can tell you that yes, there is a chance that you'd get it orally if you don't already have it, and yes, you could also get it genitally from oral sex.
She is only infectious from her mouth, assuming she has it orally. Since she has had no genital symptoms, statistically it's an oral infection. Vaginal sex is not an issue here.
If she has it genitally, it only sheds 3-5%, so it almost never transmits that way.
There is no way to predict that if you got it orally, that you'd ever have symptoms or not.
Most people with ghsv1 find it nothing more than an occasional nuisance. Many never get more than 1 outbreak, and never transmit it.
However, you have to decide if you are okay with these chances. I have genital herpes type 2. My experience with it says that herpes - oral or genital - is never a reason to end a good relationship or stay in a bad one. With hsv1, chances are really good that the next person you meet will also have it, as will the person after her.
If you find yourself freaking about hsv1 - and some do - then let her find someone who won't. That's only fair to you both.