Your daughter has set a real challenge for you ;-)
For 16 years she was used to being the ‘baby’ and that came with a kind of attention that is always left for the last child in a family. She expected to have that attention for the rest of her life, so it is easy to understand that her immediate reaction towards the baby will be resentment for taking her place as the youngest.
Add to that the fact that your daughter is at an age where she needs to accept and explore her own sexuality, and her every waking moment is filled with talk about babies - not only from her sisters, but now also from her mom. That could be confusing to say the least. On top of that she cannot in any way deny the fact that her parents are sexually active and that they now need to bear the consequences - something that we can now smile about, but we all went through that stage of major embarrassment about this, and your daughter is not exempt from it.
For your two elder daughters having babies and having sex is part of their lives, so of course there is no major adjustment for them to make.
I suspect your key to the situation is to be very clear about what your youngest values - what is most important in her life? Then you will need to find a way to present everything related to the baby to her in a way that will make her see how she can benefit from the situation.
For example, let's say she is very concerned about losing your attention because you will be focusing on the baby. You can tell her that having a teenage daughter with her own interests will be quite a relief for you, because at least you can have adult conversations with her when you get sick and tired of baby talk.
You could discuss with her the nature and level of support she is expecting from you, and ensure that she perceives herself as the ‘winner’ in terms of what is really important for her.
Right now she probably finds it difficult to express what she is angry about, because she does not want to be seen as selfish. You may have to put her emotions into words for her, e.g. "I guess you are upset because you are worried that we will spend money on the baby rather than on your college activities". Even if she does not talk to you right now, when you put her emotions into words for her, she will probably quickly tell you whether you are right or wrong. That will give you clues as to what she really values and what not.
Regardless of what happens, you need to still apply the normal discipline that she is used to. There is no reason to change the rules in your house right now, and having the same stability and rules will help her retain the structure that she is used to.
Above all, love her and she will come round to the thought of having another sibling.