I told my DD she needs to find a new place by the first of the year UPDATE
Long story short we caught my DD sneaking a boy out of our house in the middle of the night. She is 19. This was not the first time or even the same guy as the other times. Secret overnight sleep overs are not allowed. We dont have many rules but one of them is that I want to know who is in our house at all times. I dont think that is too much to ask for. Another rule is no boyfriends spending the night. I have younger daughters also who think that if their older sister does it than they should be able too also. The first time we found out we had a very serious talk with DD. If she wants to have sex she is going too but she can at least follow the house rules. I told her the next time it happened she needed to find a new place to live.
It might be really different if it was a long term boyfriend and they were really commited but just random guys is not something I want in my house.
UPDATE!: My DD has already found a new place. I helped her pack some of her stuff and she spent the night last night there. DH and I are going to help her move more of the bigger stuff tomorrow. We had a long talk and she apologized for what she did and thanked me saying that she really loved her new place and was thankful for the push getting her there.