I think my Daughter is having with her Step-Dad. What should i do?

a little background.... i am 35 years old married to a very handsome 30 yr old Medical Student and i have an 18yr old daughter from a previous marriage. My daughter and I have had a rocky relationship for the past 3 years ever since her father divorced me over my affair with my current husband. My daughter has Never forgiven me for cheating on her Dad and till this day harbors a great deal of anger towards me. I have to admit the affair was of my design ,my choice, and done with an intended purpose to marry this extraordinary handsome medical student. But at the time i didn't fully realize the cost of my actions. After my affair became known i was summarily divorced from my Ex and he moved to France. With my aim accomplished being happily married to my lover i was finally content but sadly over time i realized the cost of my actions was the relationship with my daughter. My daughter who was 15 at the time of the divorce held alot of anger towards me and swore she would make me suffer the same pain her father suffered. And true to her word soon began flirting with her Step-Dad as soon as we married a year later. My daughter being physically mature for her age began all of a sudden to wear very revealing clothings around her Step-Dad, always called him "Daddy" never refered to him by his first name which ticked me off, she would drop forks or pencils in the kitchen and bend over alot trying to brush up against her her step-dad while he would be cooking, in the summer she would walk around the house with just shorts and a bra which really got on my nerve but the final straw was when my husband was in the pool and she asked him to help her with her swimming while she was wearing a G-String! That not only infuriated me but frightened me as well. So i sought counseling for both my daughter and myself with a Psychiatrist in hopes that our relationship could mend. But to my dismay it had no benefit whatsoever. My daughter continued her various forms of flirtations with my husband for the next 3 yrs until she graduated from highschool and got into a very good University out of State based on a Cheerleading Scholarship. I was so soooooo relieved that she would be leaving the house, would be far away from my husband,she would have her dorm , everything would be paid for. And I thought her being off to college would help her finally move on with her life, find a boyfriend and just let go of this vendetta. But to my horror my daughter decided against going to the Univeristy that offered her a full ride scholarship and instead attend the same University that my husband is doing his medical residency !!!!! Her decision really reaaaaally shocked me and has frightened me very much in how deep her resolve is to make me suffer. She moved out of the house 6 months ago moved into the dorms at the college of her choice and has visted her Step-Dad every day at the hospital!!!! My husband is very transparent and forthright with me according to him she has asked him repeatedly to conduct physical examinations on her claiming she has cancer or god knows what other bullshit illnesses she has made up. My faith in my husband's loyalty to me always got me through my daughter's flirtations with him but lately things have changed. And now im not so sure. To be quiet honest i think my daughter has Finally Seduced him and having with him. My husband for the past 3 weeks has been coming home repeatedly later than usual and he smells alot like my daughter's perfume. Moreover, my husband and i for the same past 3 weeks have been having less together. Usually, we have 5 times a week now it's like only 2 times a week if im lucky. And women know that if your man isn't getting it in the bed from you he is getting it from another woman. And i am terrified that the other woman is my daughter. I don't know how to to even approach my husband on my suspicion. I can't even murmur it to him. I drove to my daughter's dorm and asked her if she has been having with her step-dad all she did was wink at me and slam the door at my face. Please can someone counsel me in what i should do ????