new female bird in the cage, the couple finches doesnt like her, is this normal?

Question
i have a couple of finches (male and female) living together for over a month, i just got yesterday an all white female finch to the cage. They seemed not to like her, at the beginning they were fighting a little bit, didn't let her eat, i place three food containers, just to make sure they let her eat, even though she is eating too little. the male is not singing, he used to sing all day long. last night the couple sleep in the nest and she was kept outside. Is this normal behaviour, should i take her to another cage? what behavior should i expect? the cage is not that big, it is around 16"x22"x12". thanks a lot.

Answer
Hi Rossana,
I would suggest getting a bigger cage if you can..and possibly another male.
 It's normal for a newcomer to be picked on a bit,but they do need a bigger space,this way they could get farther away if a nasty fight does break out.
 Good luck,Elizabeth