This is the 15302nd most frequent Russian word.
постаралась
Tried; made an effort.
The verb 'постаралась' is used here to indicate an attempt or effort made by the subject to accomplish something.
Я постаралась закончить проект вовремя.
I tried to finish the project on time.
The word 'постаралась' in this sentence shows the subject's effort to avoid causing a certain outcome or effect.
Она постаралась не разочаровать своих друзей.
She tried not to disappoint her friends.
'Постарались' is used here in plural form to indicate a collective effort or attempt to achieve thorough preparation.