Could we run into legal problems in DR later in the future for not sending her back?
yes. I would say that you are already running into problems with the DR government.
You only left with a poder de salir, right? Your husband does not actually have custody? or does he? The child has only been with you for a couple of months. Did you cut off contact with her mother?
Was this part of the marriage arrangement? Did you expect that would have both a husband and a child?
She seems very young to be away from her mother.
I know that lots of the men here will post that the women are only using the children to get money but I know lots of women here who are raising their kids alone and simply are not like that. If she wanted money from you, I doubt that she would have involved the DR consulate at this early stage.
Am I right in assuming that the child came in under your husband's fiancee visa? So that you essentially have married and adopted the child without really having a custody agreement in place?
It is very difficult to get a K2 visa, probably even more so with a child.
Dominicans are taught that the US is the land of opportunity and that a US Visa is the key to the kingdom. So I am sure that the mother thought she was really doing the best thing for her daughter and is now missing her.
So what can you do? What should you do? You really need to reach a custody agreement with the mother first. I am surprised that you got a K2 visa without having a custody agreement in place.
Did you cut off contact with the mother?
If the child is still talking with the mother every day and you still got this notice.. then you are in for a life time of trouble.