She is lazy.
This sentence is incorrect, and has already been corrected on tatoeba. It should be either Αυτή είναι τεμπέλα (She is lazy) or Αυτός είναι τεμπέλης (He is lazy). ‘Τεμπέλη’ is masculine singular accusative, genitive, or vocative, and cannot be used with είναι in this sentence. Caveat: perhaps it IS used idiomatically, as a deliberative contravention of good grammar, but I am not a native speaker, and would not know.