You are going to have to come clean to your family sooner or later, and I would do it sooner.
Because you think it's wrong, then everyone else has to think it's wrong? Of course this could not have continued for long.
She misses her parents but if this is one sided only your husband wants her there than she needs to come to an umderstanding that you are not her parents and she needs to have her own life.
anytime men and women come together, share lots of time, and are romantic towards one another they can feel feelings of 'love' blossoming.