I have read so many negative things about FB and how it has interfered with MR due to the fact one of the S will try to hook up with someone from high school or college days. In some cases, it is their way of escaping reality and trying to recapture a time when they were happy. So many people are reconnecting with old BF/GF and it's just crazy!
So, who knows what your W may be trying to accomplish, but it would not be healthy trying to figure her out. I don't think you are doing that as much as a lot of men do....and that's wise.
Yes, I think your answer to her questions about protecting yourself is what the experienced on the board suggest.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!