CP: My dilemma is this: should I just let things continue as they are (since they are so young and it will probably fizzle out long before I really need to be worried), or should I prevent their interaction as much as possible without outright forbidding her to date him? I don't want to just forbid it because I think that would pull her away from me, and we are very close.
Great questions, CP.
And your further elaboration paints a very different picture of things from the limited information in your OP. Thanks for explaining.
(BTW, you can only edit a post for about 1/2 hour after you initially post it. After that just add a new post to continue the conversation exactly as you have done.)
Have you shared your concerns about the religion with your daughter? Perhaps you should encourage her to do her own objective investigation of it. She could compare what she finds to what the boys says and to what his parents say. Then you can help guide her choices. This will teach her important life skills while keeping the lines of communication open between the two of you and not push her away or drive her “underground” into deception and/or trying to hide the relationship from you.
You might even gently point out the significance of the fact that the boy feeling that he has to hide some of his actions from his parents is a serious, red flag -- a warning that should not be ignored!