Green’s Dictionary of Slang

a lunatic vagrant.

1654		Mercurius Fumigosus 10 2 Aug. 95: How like you this sport my bonny Besses of Great Bedlam?
1676		‘A Person of honour’ The courtier’s calling 87: [A] Saint, who findes himself burthen’d with a Wife as Ugly as the Devil, and as mad as Bess of Bedlam.
1686		The devil of a wife 45: Butler. Why? here's a Madwoman falls a beating and lugging us, and calls her self my Lady. [...] Nell. I warrant it is a Bess of Bedlam.
1821		W. Scott Kenilworth III 7: Why, what Bess of Bedlam is this, would ask to see my lord on such a day as the present?
1845		Cork Examiner 22 Aug. 3/6: After a hard struggle the boats came in in the following order:- Bess of Bedlam (1) Mad Tom (2) Daft Davie (3).
1864, 1867, 1870		Hotten Sl. Dict.
1882		Sydney Sl. Dict. (2 edn) 1: Bess-o’-Bedlam - A lunatic female vagrant.