Upvote:4
If her Visa type does not explicitly preclude multiple entries, there should be no problems.
I had entered at least thirty times with a L1 Visa I had, and the immigration officers never asked why I entered so often. They always ask where I was, why, and for how long.
But, as a more literal answer to your question: yes, she can be denied entry. Any non-US-citizen can always be denied entry. No Visa and no situation gives perfect protection, it is the decision of the immigration officer.