Riley's emotions aren't controlling her, they're more like the punishment/reward mechanisms of her brain. Riley decides to do something and then gets sad afterwards, or happy, or angry. It's only when her emotions are out of balance that she is overwhelmed by sadness and loses control. I do agree that the perspective of the film makes it seem like the emotions are calling the shots and we don't see enough external emotional regulation, like from her parents. I'd also have liked it if Riley herself could have turned the ship somehow at the end. I think having the emotions control the memories was a mistake, they should've been separate mechanisms, maybe feeding into each other at most. That way Riley could recall happy memories by herself and influence her emotions. But that is a bit of emotional regulation that a child might not have learned yet.