Most Helpful Guy
She should get in contact with a lawyer as soon as possible. She should speak with the lawyer about the process by which she was evicted (is she sole or co-owner and thus cannot be evicted, was she not given proper notice of eviction, etc.) and about the way to re-establish access to her child.
With that said, here's what I would do: get my lawyer to nail their asses to the wall. To hell with all discussions about "trust [that one will remain monogamous]", because that kind of trust has no bearing on the question of whether my child deserves to have me be part of their life. Anyone who tried to deprive my child that way will be subject to everything the law can bring down on them.