Finding a London job that sponsors a visa

My friend has been looking for a job here (unsuccessfully) and needs to be visa sponsored. She's looking primarily for a PA/assistant job in a gallery. Is there any specific area on which she should be focusing? Is there any likeliness she could be hired in the art world? She comes from the nonprofit/community aid sector.

PS. i'm aware of the incredible challenge this poses (currently in a role and have been looking for a new one for 4 years)- please no snark. Just want to help a friend