Is Poor Unfortunate Souls (The Little Mermaid) a good audition song for Mrs. Lovett (Sweeney Todd)?

Both are dark and suited to the same character type and lie within the same vocal range so that's a wise choice. I would also suggest any part of Les Mis sung by Mme Thernadier, unless you need a whole song as that is more in the style of Sweeney Todd but if the audition is soon and you don't know Les Mis stick with Poor Unforntunate.