This is the 226th most frequent Catalan word.
alguna
"Alguna" means "some" or "any" in English.
Here, 'alguna' functions as an indefinite pronoun to specify an unknown or not explicitly stated object.
He vist alguna cosa interessant a la botiga.
I saw something interesting at the shop.
'Alguna' acts as an indefinite determiner paired with 'vegada' to indicate an unspecified time.
Potser vindrà alguna vegada la setmana vinent.
Maybe he/she will come some time next week.
In this sentence, 'alguna' is used as an indefinite adjective to describe the noun 'amiga', signifying one or some out of a group.