Think it having triplets can take a lot of of a ewe, and if she has been short of feed leading up to their birth she will be energy depleted. Our last ewe to lamb had triplets for the first time, she is an 8 year old ewe and our commercial ewe - mostly texel, she was only picking at her food for several days prior to lambing, managed to get her eating soaked sugarbeet for energy but she had stopped eating ewe nuts. When she finally did lamb she didn't seem to have enough energy and had to have assistance, having lambed though she is starting to pick up. Certainly made far more of a meal of lambing triplets than our Zwartbles, and its rare that they would stop eating when carrying three.
We always give our ewes and electrolyte/energy boost drink/feed post lambing which they generally love at this time and it seems to pick them up. We include limestone flour, Magnesium sulphate, lo salt, bicarb, glucose and malt extract, this is mixed with some well soaked sugarbeet and plenty of warm water added. Hopefully with some energy drench your ewe will pick up and start eating, our texel x ewe is now eating 3 feeds a day and has certainly found her appetite again.
If you are giving her a vitamin shot you might want to include B12 which is an appetite stimulant, Intravit provides B12, I am not sure that Combivit does, although it has the other B vits in it. Hope she picks up soon.