The guard is a muggle. Probably. She was expecting something with an enchantment like the Leaky Cauldron. Maybe if she continues not to see anything relevant for a while.

She catches the word "muggles"...

Ooh where.

A plump woman talking to four boys, all with flaming red hair, and holding a small girl's hand. Each of them is pushing a trunk like Dorea's in front of him, and they have an owl.

Excellent. She approaches them.

"—not old enough, Ginny, now be quiet," the woman says to the small girl. "All right, Percy, you go first."

What looks like the oldest boy marches toward platforms nine and ten, and just as the he reaches the dividing barrier between the two platforms, a large crowd of tourists comes swarming in front of Dorea and by the time the last backpack clears away, the boy's vanished. 

Ohh, that makes sense. She--should probably not cut in front of them. She might as well say hello while she's waiting for them to finish.

"Hello," she says when she reaches them.

"Fred, you next—oh, hello, dear."

"I'm not Fred, I’m George," says half of a pair of twins. "Honestly, woman, you call yourself our mother? Can't you tell I'm George?"

"Sorry, George, dear."

"Only joking, I am Fred," says the boy, and off he goes.

She waits for everyone else to be clear and then goes through.

The other half of the twin pair goes first.

And then a boy her age, and then she goes through the solid-looking unsolid wall—

A scarlet steam engine waits next to a platform packed with people. A sign overhead says Hogwarts Express, eleven o'clock. Behind her there's a wrought-iron archway where the barrier was, with the words Platform Nine and Three-Quarters on it.

Smoke from the engine drifts over the heads of the chattering crowd, while cats of every color wound here and there between their legs. Owls hoot to one another in a disgruntled sort of way over the babble and the scraping of heavy trunks.

The first few carriages are already packed with students, some hanging out of the window to talk to their families, some fighting over seats. 

When she's gone through the boy's there, a bit to the side, waiting. "You're a first year too?"

"Yeah."

"Cool. I don't know any other first-years yet."

"I met one in Diagon Alley but he was a prat."

"Who was it?"

"Unfortunately he was too busy being a prat to introduce himself."

"Oh. I'm Ron, by the way. Weasley."

She grins. "If I tell you mine promise not to drop anything?"

"...sure..."

"Dorea Potter."

Blink. "Really?"