Some girls are brought up thinking that may be dirty.
She may feel she is not clean enough for that;
Even though she is and smells good.
You need to take your time with her make her feel
comfortable about it.
For awhile just kiss around all over her body, between her
legs (on her thighs). But leave her alone in that area. I bet soon,
if you are doing it right she will let you, maybe even put your head there.
Good Luck