Interesting.....
Once again, I have no insight into this issue, And with that in mind Di, all I can advise is be calm and patient. I have no idea of the growing speed of this Bryopsis, but I'm sure you will have enough time to wait for your cure before it does serious damage to your tank.
With what you have said in your last post, if it was dormant for an extended period of time, I would assume that's because it was missing a link to thrive, now it has that link to grow and multiply, so if the dormant theory is correct, what has changed?
once again this recommendation comes without any research, but I wouldn't touch it or disturb it, to maybe slow down the "spreading" process. leave it be till the cure arrives.