How are you "managing" that? given that her stomach is the size of a small peach, its sometimes hard to manage. Does feeding trigger her cough? If so, the best way to manage it is to feed for about 30 seconds or until she's taken the initial let down. If sitting her up at that point triggers her coughing, and she then vomits, then the chances are that if you feed her again, straight after the first vomitting, then she will keep the second feed down long enough for it to absorb.
If that works, then each feed has to be in a two-step process. Unfortunattely, its the first part of the feed which is the watery part, so perhaps another thing I'd try is expressing the first part of the feed from the other breast as you give her the other side. It requires major organisation and you will feel like a 20 armed paper-hanger. If you have that in a bottle, and she will take that as well, you might be able to keep her hydrated.
But a warning. What you are doing is building up a huge excess of milk, in order for her to keep down enough to hydrate her. When she gets over the peak and things settle down, you will have far too much milk, and that may result in an overfeeding problem.
But for now, if you can build up an excess, and just keep feeding her as much as she will take, and try the double-feed trick, maybe you will find a way to keep her hydrated.
In terms of weight loss, how much has she lost? She canot do better than on breastmilk, so there aren't too many options there, because what you have, is the best thing for her. Given that there should be only another three weeks of this, she should be able to ride it out if you can keep her hydrated, and then she will catch up later.