Well if the key is Db and the root of Mary's chord is also Db, then it looks a lot like an inversion of a partial Db13; the 3rd and the Dominant 7 are missing. Did I get that right?
Next question... The Bb could be the 13th or it could be the 6th. Now I've seen references to 6/9 (six-ninth) chords. What's the deal with those and could Mary's chord also be called a Db6/9?