It amazed me because your daughters is too young to have a boyfriend. Maybe you can invite them yo your house or find about her BF information and what their parent look like personally. Especially if their boyfriend have a large gap in age. I know a lot people will tell you to trust your daughter. You may trust your daughter, but do you TRUST her boyfriend? ask this questions to yourself.
You could let her go, but make sure that there are other people home as well, for supervision. And never let them close the door if they are going to chill in a room, they are too young to be alone. that's my opinion.