Female.The word "gender" only applies to the term, though. People don't really have a gender, they have a sex. Gender is more applicable to French, or Spanish, where every noun is either masculine or feminine- le mur, la ciel, etc. That is the proper use of gender.
Female
Connotatively, there really isn't any term that fits. Probably, the closest thing would be a "confirmed bachelor," but that has a suggestion of freedom, whereas "old maid" suggests unfulfillment.
Maid of honor
Usually female.
The gender of a lady servant is female. Some nouns for female servants are housekeeper, lady in waiting, maid, milk maid, house maid, or domestic.
maidservant
A maid.
Butler
The term servant is not usually gender specific and is a universal title. To make it gender specific for female use maid.
No I'm not an old maid.
It is a maid servant
maid of honor.