As in this Dispensation consultation with expert doctors is highly advisable and acting in accordance with their prescriptions obligatory, it is well for her to undergo an operation if deemed necessary by such doctors.

‘Abdu’l-Bahá, The Compilation of Compilations vol. I, p. 470

Observe the human body, its limbs, its members, the eye, the ear, the organs of smell, of taste, the hands, the fingernails. Notwithstanding the differences among all these parts, each one within the limitations of its own being participateth in a coherent whole. If one of them faileth it must be healed, and should no remedy avail, that part must be removed.

‘Abdu’l-Bahá, Selections from the Writings of ‘Abdu’l-Bahá, p. 190

Before having any serious operation, you should consult more than one qualified physician.

Shoghi Effendi, Lights of Guidance, p. 291

The Guardian advises that you should refer to other doctors, and follow the majority vote.

[1 This advice was given by the Guardian in a case when the inquirer sought the Guardian's counsel, since one doctor's view was that an operation was needed, while another doctor did not consider such an operation necessary.]

Shoghi Effendi, The Compilation of Compilations vol. I, p. 106