You can consider her mascot but she's still joining
Not even that. Chopper is the mascot.
She's just a bad written character.
Let's do a pop quiz: Does Yamato had friends? What about the number?
Does Yamato grows up going against Kaido? So why every beast pirate knows her and thinks she will lead in a moment of crisis and why Kaido took the time to tell her about his fruit (she even knows more about the fruit than a user)?
Did she live in hunger and despair because of opposing Kaido? So why the first time she is even mentioned she was invited to a banquet as a everyday thing to celebrate his victory and no one batted a eye?
And so on and so forth. She just exists to introduce plot points and hold the lines until a better character appears to solve the issue.