This is the 7193rd most frequent Polish word.
jankina
"Jankina" is not a standard Polish word. It may be a proper noun, regional term, or misspelling.
Here, 'jankina' is used to describe a characteristic of the friend, specifically her connection or association with Janka.
Spotkałem się z jej jankiną przyjaciółką.
I met with her friend related to Janka.
The word 'jankina' here is a possessive form of the name 'Janka', indicating that the bag belongs to Janka.
Jankina torba jest bardzo ciężka.
Janka's bag is very heavy.
In this sentence, 'jankina' is used as an attributive adjective derived from the name 'Janka' to denote possession of the book.