Setting Limits

As I have mentioned before I have a teenage daughter who has a steady boyfriend. For the most part Iam ok with this (its not like I have much choice!). Our family is holidaying at the moment at the beach and BF has been invited to stay with us. I didn't foresee the amount of time they would spend together to the exclusion of all else. In a way its sweet how devoted they are to eachother but I have to admit it's really starting to get on my nerves. I am the WORST parent in the world because I have said they aren't to spend any time alone in the bedroom together. We share our holiday house with another family and the whole lot of us sleep in the same room (except BF, he's on a swag on the lounge room floor). I'm really struggling with setting limits that we can both work with and accept. To be honest I'm really struggling with setting limits at all. I'm so new to this! I don't know what I'm doing! I want her to be responsible for her own decisions but I also want to stop her from making any bad ones. And her idea of a bad decision differs quite a bit from mine! Honestly, I just didn't realise it was going to be this hard. I apologise profusely to my Mum for putting her through this!

Dear Lord. I really need your help here. Help me to find the right words to help my daughter understand that I only want what is best for her and my only aim is to protect her. Help her make wise decisions and respect herself.
Amen.