It may have been an OM, but then something you've overlooked is it could of been for you then she realised and wanted to get away again given what she said tin the other text. However, it could of been for her sister as she has said but if it doesn't matter and it's a symptom as you say and you can handle the knowing and saying nothing, do it. You lose nothing by knowing.
I have an opinion, but my opinion is clouded by ahwat happened in my own sitch. However, I'm a believer in gaining the evidence before questioning your W so you know for definite.
I think you have got back on the roller coaster because of this text which is understandable. Try and get yourself a bit of space away from the triggers (your W) if you can right now and keep yourself really busy. Your W may even bring up the text at Mediation so you might get the answers there.
