Oh soul you are such a great mum, I cant believe how cool and calm you are being and trust me it will all work in your favour, you sound like you have such a great relationship and she may even let you know when and if she does start the physical side of things. Maybe discuss the pill and say that you really want her to go on the pill a couple of months before she starts having sex and then when she comes to you wanting to go to the dr at least you will know (just an idea)

I have 4th daughter on the way and this has been on my mind for a long time (still have a while to go until Im where you are i hope) it is really hard to imagine them having a relationship let alone sex.

Good luck you are doing such a great job!!