She's probably having multiple lambs, I've seen this a lot with ewes having triplets. Given the timing it is far more likely to be that than scab. Does she look wider than the others?
Give them all a high energy lick and make sure she's getting her share of concentrates. If she is shy and hangs back until the others are done you may need to feed her separately.
Also, get in some calciject 20% in case she needs it after birth - ask your vets advice on how, when and if to administer it, it's not that I don't know when myself, I just think it best administration advice comes from your vet. Vets usually give advice free and will explain how to correctly inject it.
As regards the wool, if you can avoid pulling any out when you handle the ewes it will hopefully sit on her back until the weather is warmer. An elderly shepherd friend of mine told me once that when the wool comes away spontaneously like that it doesn't seem to ill affect them in the way it would if you sheared her. It does seem to be true. Hopefully she will keep enough of it to cover her back but if it snows, I would make sure there is some shelter out of the weather for her.