The Collaborative International Dictionary of English v.0.48:

landlady \land"la`dy\, n.; pl. landladies. [Cf. landlord.]
   1. A woman having real estate which she leases to a tenant or
      tenants.
      [1913 Webster]

   2. The mistress of an inn or lodging house.
      [1913 Webster]

WordNet (r) 3.0 (2006):

landlady
    n 1: a landlord who is a woman

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "landlady":
   beneficiary, cestui, cestui que trust, cestui que use, deedholder,
   feoffee, feudatory, hostess, householder, laird, landlord, lord,
   master, mesne, mesne lord, mistress, owner, proprietary,
   proprietor, proprietress, proprietrix, rentier, squire,
   titleholder