This is the 3446th most frequent Russian word.
присоединилась
"Joined."
In this sentence, 'присоединилась' indicates that the subject joined or accompanied a group of people in their activity.
Она присоединилась к нам на прогулке.
She joined us for a walk.
Here, 'присоединилась' means that the subject became a member of an organization or group.
После некоторых раздумий, она присоединилась к клубу.
After some consideration, she joined the club.
In this case, 'присоединилась' refers to a bird physically joining a group of other birds in their movement.