Skanky summer intern hitting on my husband?

My husband's company brought in summer interns in May, and my husband chose to mentor this little perky blonde from the local college. She is always calling him on his cell for "help" and at a company barbecue I went to with him, she kept touching and flirting with him. I heard from one of his coworkers that she even invited him to lunch. He ures me that he is just being a good mentor, but I want him to get rid of the little witch. Why is this tramp trying to ruin my marriage and how can I get through to him?