This goes well beyond simply being a lesbian child dispute, the biological mother and birth mother are two different people. That doesn't often come up in a breakup of a relationship and the legal implications may well break down into semantics.
But it does seem like there was some dickery involved in the relationship and custody battle that generally get the kid assigned to one or the other on a lasting basis, without visitation. That whole wandering off with the kid thing could be written off as kidnapping and has been in at least one case I've read about recently.