"Amber is going to nurse off you, just as you would expect of your baby." is the Nurse's pronouncement.

Sounds fine to you, and you open your arms to expose your massive breasts, which you notice are bigger than normal. [Didn't you read somewhere that is an effect of pregnancy?] Your milk has come in already? Apparently so, as Amber climbs on top of you and kisses a nipple before she starts suckling. You quickly feel a stream of milk entering her mouth.
It gives you a very nice feeling, and you start having very motherly feelings towards Amber. You hug her tenderly and position yourself so she can drink better.
Still not everything is perfect ... "I don't even get to name her? I am her mother."

Cassandra does not budge. "She was named long ago. Besides, you like the name, Amber, right?"

You are not sure you would have agreed an hour ago, but there can be no flaw to your wonderful daughter. She is perfect. So her name must be perfect too. Therefore Amber must be the perfect name. You are not sure that is sound logic, but as you caress her lovely blond hair, which is perfect too, you don't care. Instead you bend forward to give her a kiss.
This allows you to realize something is happening. Your breasts have vanished. You are as flat-chested as a boy. Yet Amber continues to nurse. She has not only drank all the milk you had, but she, no... you have converted your breasts into more milk for her to drink.
That is not the whole of it. You realize your feet are gone [or rather, are now just empty skins], also converted into milk. Every last bit of you is being converted into milk for Amber. This really ought to horrify you, but this is milk for Amber. The more you can do for your wonderful daughter, the better. You happily urge her to drink more.

She does. She drinks hard and long. And you keep supplying the milk as fast as you can convert yourself into milk. But there is only so much of you and you eventually feel Amber trying for more, but nothing comes.

"Empty" is Amber's first word. It's an apt description of you. All that's left of you is an empty skin. You try to tell her you are sorry you can't give more, but find you have no muscles to move a tongue, which is no longer there either. All you can do is lie there. "Well, I guess that's enough for now. But what do I do with what's left of Mom?"

"Well, you can have your first solid food by eating her. But if you are full, you can give her to me and I can convert her into a rug."

"OK, I'll..."