Bree is trait positive hence why The Order wants her so bad however, they are going to need future trait positive people to continue on with the ceremony and such...
So the only way to guarantee this is for her to have kids with another trait positive person. So, if Jonas really is Bree's brother like many have been speculating, he would most likely be trait positive also. Bree would have had to keep her purity bond until the right person came along (a.k.a. Jonas).
We know that the old Bree would have never EVER taken anything far but with her most likely still being under the control of The Order, this may have been their plan all along. They could have programmed her to respond to Jonas and to be very *ahem* friendly with him. It actually seemed in the video that Daniel was getting a more genuine response out her instead of Jonas, at least for me it did.
We know that the ceremony also probably involves a lot of blood and the stuff in her blood "gives life"...
I know it seems a little crazy but it does seem to fit....

