Spouse of birthfather and pending reunion

I am the wife of a Birthfather who reached out to his daughter last year. She is a 26 year old adult now. Her mother and stepfather raised her and did not tell her she was adopted (by the stepdad) until she discovered papers during her adolescence. My husband knew nothing of those details until the birth of the all the social media allowed him to search for and contact the mother. I am very supportive of any relationship they can build and we are both anxious to welcome her into our family (2 grown children are mine, 2 young children are his with his exwife). After contacting the mother, daughter waited a year before she felt ready to reach out through email. Not long after, they exchanged cell phone numbers and began an exhilarating 'getting to know you' texting session that, while in the beginning seemed to be beneficial and informative, became difficult to maintain as his daughter began to grapple with alternating feelings of anger toward him for the abandonment, anxiety and general identity crisis issues. The texting was going on until 2 or 3am with Birthfather feeling afraid to dial back communication for fear of exacerbating her abandonment issues. A meeting was planned in spite of the volatility in communication although attempts were made to reduce the texting and instant messaging prior in order to achieve a more comfortable balance. He urged her to seek counseling and we consulted a therapist to help guide us into the meeting. The meeting is in two days, but it seems it may fall apart before it happens. On the counselor's recommendation, he asked to stop the texting and to change some of the expectations previously set for the meeting. Originally there were loose boundaries around the timing and activities (planned weekend visit with Birthfather in hotel, potentially letting her stay in a nearby room if conversation went into the night). Counselor advised against that and suggested much more care and a slower pace - to allow a relationship to develop. Upon communicating that to her, she has seemed to interpret rejection/abandonment and he is now uncertain she will want to meet him at all. This is all so heart-wrenching and confusing. He wants to be a positive, he encourages her to continue to seek counseling and he will, too in order for them to try to develop a healthy relationship over time. If she pulls completely back, after seeming so enthusiastic about knowing him, should he leave her alone or continue to push on with attempts at email contact periodically? What, if anything, should I - as his wife - do in the way of helping her know how welcome she is in our lives? Thanks for listening....