There are 2 titles associated with this person.

@book{ wphp_3281
  author={Nihell,Elizabeth},
  year={1760},
  title={A treatise on the art of midwifery. Setting forth various abuses therein, especially as to the practice with instruments: the whole serving to put all rational inquirers in a fair way of very safely forming their own judgment upon the question; which it is best to employ, in cases of pregnancy and lying-in, a man-midwife; or, a midwife. By Mrs. Elizabeth Nihell, professed midwife.},
  publisher={A. Morley},
  address={London},    }
@book{ wphp_3371
  author={Nihell,Elizabeth},
  year={1760},
  title={An answer to the author of the Critical review, for March, 1760. Upon the article of Mrs. Nihell's Treatise on the art of midwifery. By Mrs. Elizabeth Nihell, Professed Midwife.},
  publisher={A. Morley},
  address={London},    }