The one sidedness and drooping lip etc sound typical of Listeria.
It is a bacteria that can grow in forage, usually silage, but isn't always noticeably 'off', and potentially could be carried in hay.
It enters individual animals that may have a small cut etc in the mouth, so is usually a one-off, but if concerned, burn any hay that may be suspect, but like I say, it's unlikely to affect anyone else.
Penicillin is the only antibiotic I know of that is effective against Listeria, and an extended course at high dose is necessary, so she's on the right treatment.
Mortality rate is commonly high, but I believe this is at least partly due to it not being commercially viable to nurse a single sheep through it.
I have nursed a ewe through Listeria when I was a meagre vet student on lambing placement. She lambed early (according to raddle by at least a few days) and was brought in, was dropping cud from one side, falling over the same side, and generally a bit off. Bottle fed her lambs, kept her in in a pen so she couldnt get into trouble for a while, then she went out to the 'hospital field' that was getting extra checks due to triplets/fosters/weak lambs/ewes, and a few days later she was the bugger that escaped out the gate when I was trying to get another sheep in, seeming none the worse for wear, and by this point feeding both her lambs.
Bear in mind Listeria can also cause abortion, so she may or may not lamb early, or produce dead lambs later if the bacteria has affected the placenta, just a warning so its not such a shock, keep a close eye on her.
Hang in there, and best to keep her confined until she is able to get about without too much staggering so she won't get into trouble outside, and maybe see if the vet has some ointment for her eye.
Sounds like you're doing everything for her, and certainly the energy liquids and calcium are always good as a general pick me up in a ewe late in pregnancy who is struggling to eat/drink.
All the best
Suzanne