The correct answer has already been given several times - it's acetone. It's cheap and available at almost any hardware store or beauty supply store. I'll bet your wife already has some. A lot of nail polish remover has acetone in it still. I just looked at my wife's, and it says "100% Acetone".
I have a can on the shelf from Home Depot specifically for cleaning up spray foam "incidents". It was $5.00. Her bottle from Sally Beauty was $1.59 (The same amount I got from HD for $5.00!!!). -- If someone refers to herself / himself as a "guru", they probably aren't.