I am told that a female is not allowed to cover her face when in Ihraam.

Answer

It is correct. A penalty has to be paid. If the face is covered for a full

24 hours, one dumm is Waajib. That is, one sheep/goat has to be sacrificed in the Haram area and the meat given as Sadqah to the poor. If less than one quarter of the face was covered or the full face was covered for less than 24 hours then the Sadqah Fitr amount (approximately 2 kg of flour or its equivalent price) should be given to a poor person.