tixylix won't help if it is croup, IME but you could try it if you want
Also do NOT give her medised - kids that struggle to breathe in their sleep (as per a croupy cough) should not take it because it is a sedative - it relaxes the muscles, therefore making it harder to breathe - my DS's nurse told me this.
Please - don't give medised (calpol/nurofen are fine)
You will need to raise the head end of her bed/cot (books underneath or something) and keep a bowl of boiling water in there as she nods off to sleep - out of reach, of course... alternitively, sit with her in the bathroom and make it fill with steam (although I prefer the bowl one cos I hate sitting in a hot room!)
You could also add menthol crystals (just one or two) to help her nose keep unblocked.
Croup does sound much worse than it is (sounds like a seal/sea lion bark) and lasts for about a week or so.
My ds got this every other week for 4 years - CAT/message me on here if you need any reassurance
Thinking of you - hope she gets well soon