Rey seems to have at least a basic understanding of Shyriiwook
All quotes from the novelization.
She responds directly to Han and Chewie
She nodded. “It’s just us.” She nodded once to her left. “Us and a droid.”
A second shape appeared above and beside their inquisitor. It was likewise most definitely not a stormtrooper. It was also much, much bigger than its blaster-wielding companion. A battery of sounds issued from between thick lips, something halfway between a moan and a question.
“No, it’s true,” Rey responded. “We’re the only ones on board.”
Finn gaped at her. “Wait— you can understand that thing?”
She translates for Finn.
She tried to find something to say to that, something worthy of the sentiment and the risk they had undertaken. She failed miserably. Chewie, however, had something of his own to add. Whatever the Wookiee had uttered caused tears to well up in her eyes. Having never found himself in such a position before, Finn was unsure how to respond. Knowing well her inner toughness, he wondered what Chewbacca had said that could have inspired such a reaction.
“What’d he say?”
She sniffed and wiped at her face. “That it was your idea.”
She again responds directly to Chewie.
“The oscillator is the only sensible target,” Finn told him. “But there’s no way to get inside.”
“There is a way.”
Everyone turned toward Rey. It was Chewie who ventured the question that had to be asked.
“I’ve seen inside these kinds of walls,” she told them as the sky overhead continued to rain destruction. “The mechanics and instrumentation are the same as the Star Destroyers I’ve spent years inside salvaging. Get me to a conventional junction station, I can get us in.”
Less definitive is their exchange aboard the Falcon
In the cockpit, Rey headed for the copilot’s seat, only to find her way blocked by a massive, hirsute form.
“Chewie, the Falcon flies better with two people at the controls, you know that. I’ve already sat in that seat. I’m ready to do so again.”
A series of moans came from the Wookiee. Then he turned— and sat down. In the copilot’s seat.
Rey felt herself tearing up. “You’re serious, aren’t you?”
Chewie groaned and, to make certain she grasped his meaning, gestured to his left. Toward the pilot’s position.