ei venninne · (female) friend
Feminine (ei)
Indefinite singular
ei venninne
Definite singular
venninna
Indefinite plural
venninner
Definite plural
venninnene
Feminine nouns (ei) can always be written with en as well: ei bok, boka or en bok, boken. Both are correct Bokmål.
How to guess the gender Nouns: gender and articles