What you told her is okay, but it depends upon the grasses she is trying to eradicate. If it is bermuda, douse it with gasoline and set it on fire. Just kidding. The newspaper layer should be separated sheets somewhat crumpled, not flat. Then a layer of compost, a layer of mulch and a layer of newspaper, over and over is what is referred to as lasagna gardening and it works quite well.
As for the vinegar spraying, the rose bush will be fine so long as there are no leaves on it (upon your writing , being that it was in January, that should be fine). Usually the spraying of an entire area that contains things you do still wish to keep, so long as they are dormant, is recommended between Christmas and New Year, but as long as it is done before budbreak, this should be fine.
Nadine Bielling Haefs
Gardener Exchange Forum
The Laws of Ecology:
"All things are interconnected. Everything goes somewhere. There's no such thing as a free lunch. Nature bats last." --Ernest Callenbach