Just for consideration--the two religious friends in the OP probably aren't bullies. If their faith teaches that the unsaved will go to hell (no if, ands, or buts), and if they believe OP's daughter to be unsaved, then they almost surely see it as right and their obligation to get her to church and to give her the message. I don't think there's any way their parents can effectively communicate to 8 YOs that "everything you heard in church is true--hell is real and the unsaved are in the express lane to that place. But, just the same, don't badger your friends about this, they need to make up their own minds, and their families may not believe as we do, we need to let them go their own way. Yes, they'll probably go to hell and burn forever in unimaginable anguish." The problem isn't with the kids or the parents, the problem is the beliefs themselves.
I think the OP's plan to talk with DD about other faiths and take her to some services is a good idea. These families are indoctrinating their kids, and if you don't take an active posture yours will be indoctrinated, too, in a way that you'd probably not like. IMO, seven years old may be a little young to start visiting churches with her, but maybe not. I'd keep the kitchen table lines of discussion open, look for opportunities to raise the issue, and back off on the actual site tours if she doesn't show signs of interest.