There are multiple definitions - click on the translation that matches your context.
companheira means:
substantivo
partial
noun
Pursuant to sections 1,723 to 1,726 of the Brazilian Civil Code, "companheiro" is a person in a "união estável" (comparable to a common-law marriage). The Brazilian law imposes no requirement of living together in order for a "união estável" to exist.
a woman who is not officially a wife but is considered to be one in some countries because she has been living with her partner for a long time
The millionaire's common-law wife has claimed half of his assets.