Yep - have looked for Thurza, Thursa, Thirza, Thirsa, Theresa, Teresa, Thisa, Thiza, Thusa, Therza, Thyrza, Thersa, Thyrsa - she's on the 1851 as Thuza!
I've been reduced for searching for all people born in Great Bentley (or Bentley, or Gt. Bentley and however many other variations) and even those born in Essex in 1840 +/- 2 years and nobody comes up!