Welcome to the forum RunAwayDaughter.
I was happy to see Diogenesister mentioned the loss of her father as being related to her actions. That too was my thought when reading your earlier comments.
As your daughter is usually quiet and behaves in a predictable manner, perhaps the loss of your husband affected her more than you or her brothers realized. Since you were all deep in grief (understandable), she may have felt there was no one available to discuss the loss she was feeling.
The boyfriend (you didn't mention his age) likely provided her with attention and a listening ear that she needed. Unfortunately, her mental state would leave her vulnerable to being easily influenced.
While she may eventually recognize she made a mistake in leaving home, as the BF is controlling and without her own money, may feel somewhat trapped and may be reluctant to express that she wants to return home, especially when reflecting on the behaviour she had shown to you and her brothers.
I suspect her desire to want to talk to a counsellor may have been related to discussing the loss of her father, not necessarily about leaving home - not yet. Unfortunately, JWs are taught to believe psychiatry and counselling are wrong and so the JWs she is staying with may have convinced her to not follow through with the appointment you set up.