Scroll feet are found on plenty of USA Classic Carnival items (e.g. Fenton). Most European Carnival usually has a ground base, without feet. But there are examples of scroll feet from (for example) Walther, Brockwitz and Inwald. They differ from the Classic USA examples in that the European ones are (usually) ground flat.
So Della's bowl is almost certainly European - and my "gut feel" is Walther - but I could well be wrong.