It's worth helping her to stand properly every couple of hours, especially if she gets any worse. She needs to stand to pee properly and to burp, plus it stops her legs getting pins and needles. You can hold her for a few minutes, or use bales to prop her up.
Are you bottle feeding the lambs? They won't be able to feed if she's sitting, and she won't be producing much milk if she's poorly. Is what the vet gave you antibiotics? She needs them for the wheezy chest, which is a prompt killer without help.