What would the typical responce from WW be when they find out there soulmate has another girlfriend that they are hidding from WW?
I think calling OM my FWW's "soulmate" would be a bit of a stretch, but she did feel a bit betrayed when she found out that he had another GF. She already knew about his fiancee prior to the A turning into a PA (yes, the OM was involved with three women at one time). My FWW actually suspected that the OM had another GF during their A, but that did not stop her from doing what she did.
A's seem to apply an extra large dose of stupidity to the involved parties, it seems.
BTW, after breaking the news of her A to me on D-Day, she actually had the audacity to tell me that she "knew how I felt" because she also was betrayed - by the OM. I think that was probably the time I felt the most anger towards my FWW in the 20+ years that we've been a couple.