The British High Commission confirmed her death, and non-governmental aid agency Mercy Corps named her as Faye Mooney, one of its employees in Nigeria.
Mercy Corps said it was "utterly heartbroken" to learn that Mooney, who had been working as a communications specialist with the agency for almost two years, had been "tragically killed" by gunmen at the resort in Kaduna State, in the northwest of the country.
Kajuru Castle holiday resort
"Faye was deeply committed to fostering cross-cultural collaboration and was an inspiration to us all," CEO of Mercy Corps Neal Keny-Guyer said in a statement.
"We extend our deepest sympathy to those who have been affected by this senseless tragedy."
Local police said the two victims had traveled to the Kajuru Castle holiday resort with 12 other tourists, and that the attack took place around 11:40 p.m. local time on Friday.We are aware of the tragic incident involving the death of a British national in Kaduna State on Friday. The next-of-kin has been notified. The British High Commission offers our most profound sympathies and condolences to the families and friends at this difficult time.— UK in Nigeria🇬🇧 (@UKinNigeria) April 21, 2019
"Intensive efforts are being made by the Command to rescue the kidnapped persons, (apprehend) the fleeing culprits and bring them to justice," Kaduna State police said in a statement.
Officers did not state the motive for the attack, name the other person killed or release any details of those who were kidnapped.
The risk of kidnapping is high in northern Nigeria, according to travel advice issued by the UK government, where locals and foreigners have been targeted for ransom.