This is the 9501st most frequent German word.
mitfahrerin
A female passenger or co-rider.
In this context, 'mitfahrerin' specifies a female who joined the group as a commuter.
Die Mitfahrerin stieg am Bahnhof zu uns ins Auto.
The female passenger joined us in the car at the train station.
The word 'mitfahrerin' here represents a usual female participant in a carpool arrangement.
Unsere regelmäßige Mitfahrerin hat heute abgesagt.
Our regular female carpooling companion canceled today.
Here, 'mitfahrerin' is used to signify a female passenger participating in a carpool.