The "Why" Seems like more a question for the Counselor. I suppose DonH could be on to something about her needing the constant validation... that would be consistent with what W and MC have explored in IC about W's rejection-filled past. Whatever it is, it is not a new behavior pattern for her, and certainly far predates her "WW" phase. Definitely more of a concern now, though, that she is in the recovery phase from that syndrome.
I guess that is one way to look at it. The other way is that this rejection-filled past has always had her in a state of waywardness. I worry about this same thing with my wife. She too has always craved acceptance and validation. And this made her especially vulnerable to OM's advances. Since she's always kept this to online emotional affairs, she could justify what she was doing as she would "never let it go physical". Thus her OEA in 2005, and the more recent one.
I think your approach of letting MC and IC handle it is the right one. Obviously her behavior the other night is not in keeping with what needs to be done for R.
M(53), W(54),D(19) M-23, T-25 Bomb Drop - Dec.23, 2017 Ring and Piecing since March 2018