Is she having sex with anyone else? Your husband? It sounds like she is being very cautious and just doesn't want the relationship to be focused on sex, or it might be that she's new to sex with a woman and isn't confident or sure enough how to proceed. I think talking about it would be good for both of you.
The world opens up... when you do.
Oh, oh, can't you see? Love is the drug for me. ~Bryan Ferry
"Love is that condition in which another person's happiness is essential to your own." ~Robert Heinlein