Like this.

A small twig flies up from beside Saphanore's shoe and swirls around for a few seconds before neatly returning to its previous position.

I could do magic for you. Make everyone think you were a wizard too, a true princess of Elmia, instead of the disappointment you really are.

"I'm... I'm not a disappointment, that's a really mean thing to say, even if I can't do magic I'm still good at reading and drawing and, and climbing trees, and — and even if I wasn't they'd still love me, they're my parents, that's what parents do!"

It's not mean if it's the truth. May I show you one of my wizard's memories?

"O-okay... but it's not true, it's really not..."

He shows her the memory of reading a letter, slowed down to accomodate the reading speed of a seven-year-old.

Dear wizard

We're contacting you all because our daughter has now reached the age of seven without ever displaying magic, a fact we're quite concerned about. She's from a long line of wizards, on both sides, and we don't understand how this could have happened.

We're especially concerned because she needs to be queen of Elmia someday, and for that she needs magic. 

Because of this, we will handsomely reward anyone who knows of a way to fix her. A thousand gold pieces for a credible idea, ten thousand if it works.

We sincerely hope that one of you talented wizards will be able to help us.

Best regards,
Icamaion and Misuravi,
King and Queen of Elmia

They think you need to be fixed. Do you even know how much money ten thousand gold pieces is? They must want this very badly.

She starts sobbing.

There, there, child. It's not fun to face the truth. 

But there is a way you can make them proud of you again.

Wear me everyday. I'll help you pretend.

They'll be so proud of you.

For the first time in years.

"...I'll do it."

Good girl. Now dry off your tears and let's go back to your castle. Then you can show off your new skills to your parents.

Saphanore wipes off her face and starts walking. She feels very alone, like she wants a hug from her parents. Except her feelings about them are all sorts of complicated, now, so maybe she doesn't want that. 

Maybe talking will help. "Do hats have names? Humans do. Mine's Saphanore."

I have in fact chosen a name, but it's not in a human language. May I send it to you?

He'll angle for broader permissions later. Right now he'll focus on building trust. Then he can use that trust, later.

"...okay..."

My name is — and he sends the sensation of magic: a quiet hum in the air that permeates everything in existence, tingling with potential, an invisible force bending reality to his powerful will.

He was given another name, by the wizard. But he likes this one better.

Apparently the hat's name is a weird goosebumpy feeling. 

"I didn't know you could have a feeling as your name."

It takes her a few seconds to remember her manners. "Um, it's a very pretty name." 

For a kid, she's pretty good at lying. He chose her well.

It's still quite obvious that she thinks his name is more strange than pretty. It's not surprising; of course a mundane wouldn't appreciate the feeling.

Still, she praised his name, and he should respond. Thanks.

"...I'm not sure how to say it, though."

You won't need to. If you're speaking directly to me, I'll know. And you'll not be talking about me to anyone, I hope, or they'll know it's not you doing magic.

He's been listening to her for a while, now, and he's getting familiar with her voice. Just add some bass to make it sound the way she'd hear herself, and —

They'd know I'm a total failure, says Saphanore's voice inside Saphanore's head.

It's true. She's scared and lonely and needs a hug, and her parents will never hug her again if they find out. She's magicless, and they can never know.

Hopefully that'll be enough to avoid her blabbing to the first person who looks sympathetic. Can't use that trick too much, though. She might notice. It'll be safer when he has a mindreading permission, so he can make sure the thought sounds native, but even then he'll have to be careful.

When they've walked for a while, the trees start thinning, and a beautiful castle slowly becomes visible. Its white stones shine in the sunlight, and the many, many spires seem to pierce the clouds, so tall are they.

A guard stands at the gate, big red feather in his helmet, polished sword at his side. His face lights up when he sees Saphanore. "Princess!" he says. "You're back!"

"Yeah, I am." She gives Cav a quick hug. "And I —"

No, wait, she can't tell him what actually happened in the forest. Can't tell anyone. She stays in the hug a little longer.

...why did he have to pick a plan that relied on a small child's acting skills. 

If you'd actually found your magic just now, I'm guessing you'd be all ecstatic. Telling everyone about your new talent. So that's what you have to do now, if you want this to work.

He'll have to grab control of her emotions soon, or this'll all fall apart.