She picks the smaller one, of course.

"You sure?  I don't mind."

"...I'm sure."

"All right.  I oughta write Dumbledore, let him know I got you.  You best turn in."  He sticks out a hand.  "Pleasure meeting you, Harriet."

Handshake. "Pleasure meeting you. Goodnight..."

Oh she doesn't know his name.

" - blimey, did I never introduce myself?  Name's Rubeus Hagrid.  Keeper of keys and grounds at Hogwarts."

Small smile. "Night, Hagrid."

Big crinkly grin.  "Night, Harriet."

And she heads back to her new room to sleep.

The next morning Hagrid makes a fire on the beach and roasts some sausages for breakfast, and talks with Harriet a bit about her school supplies list, and asks her a few somber questions about the Dursleys.

"...They're fine," she says at first, though he's able to wiggle details out of her even without her directly willing to talk poorly of them - mostly that she isn't fed enough, and that her cousin's mean to her, and they sometimes 'get mad.'

He nods, somberly and patiently, to her explanation.

"Well," he says, "reckon we ought to get you to St. Mungo's, first thing, if you've not been getting enough to eat."

"...Where's that?"

"It's hidden in London," Hagrid says.  "Which is where we're goin' anyway.  We're gonna head to the Leaky Cauldron and get to St. Mungo's by Floo.  Folk don't usually come in through Muggle London, it'd attract too much attention."

"What's floo?"

"One of the ways magic folk travel.  Fireplace-to-fireplace.  It can be a mite uncomfortable, but it's safer than it looks."

Nod. "What's a muggle?"

“’S a wizarding term for non-magic folk.”

She nods a bit.

"Finished with your breakfast?" he asks.  "Best be off."

"Yeah, I am."

"Right then."  He stands up and claps his hand twice, and the tent folds itself back up.  He puts it and - with some difficulty - the rowboat into his knapsack.

"We'll take the Muggle way to the Leaky Cauldron," Hagrid said.  "Town just up the road has a train station, we can get to London from there.  Follow me."

She does, mostly quiet.

Hagrid draws a bit of attention for his size alone, and has a bit of trouble getting through the turnstile, but seems reasonably adept at passing for a muggle.  He passes the time on the Underground working on a knitting project, though he'll answer any questions she comes up with.

In London he leads her through bustling streets, clearing a path through the crowd, and eventually down a little side street.  He stops between a shabby bookstore and a dingy record shop - and oh, there's a little pub between them, it hadn't looked like there was anything there a moment ago -

"It looks small."