"Daddy." she says, and by this, Harry knows she wants something.
She hardly calls him Dad anymore, let alone Daddy.
It's all "Will you pass me the salt?" and "Will you lend me your keys?".
It reminds him of being with the Dursleys, when all he got was "YOU!" and "Potter!".
He hates it.
He supposes it is because of the fact that, several months ago, on Lily's fifteenth birthday, it was discovered by all that Ginny had cheated on Harry and Harry wasn't Lily's real father.
It had killed Harry, who loved his little girl and wanted to be connected to her, and it had killed James, because he felt as though she wasn't his sister anymore and cut her out entirely, and it had killed Albus, who was stuck in the middle.
But most of all it killed Lily, who felt more distant from her family than ever.
She didn't speak to James, she felt Albus wasn't loyal enough to her, she had expressed quite clearly that she thought her mother was a disgusting slapper who slept around, and, since then, she was unsure where she stood with Harry, so mostly he had been nameless to her.
No Dad.
Just you.
And, if she wanted something, Daddy.
"Daddy, please will you iron my shirt? I have to go out soon and I'm hopeless at ironing!" she tries to be overdramatic to make him laugh, but her heart's not in it - it isn't the same anymore, they aren't the great father and daughter duo they thought they were.
"OK." he swallows, his voice hoarse.
She throws it to him with a 'Thanks!' tossed over her shoulder as she runs upstairs.
Even though she protests and insists she can Floo home later that night, Harry knows he will be going to pick her up later.
She is - was - his daughter, and he needs to keep her safe.
Albus and James were always certain she was his favourite because, whatever trouble Lily got into, he was there in an instant.
With them, he took longer; when Al was failing Charms and sent an owl to Harry pleading for salvation from his Troll-grade hell, it was two weeks before Harry replied helpfully and, when James got a girl pregnant and didn't know what to do, it was a month before James was even allowed in the house.
What he didn't tell them was that he was giving them time to help themselves; that he knew they were strong enough to get through this on their own.
With Lily, she would spot a problem and run straight off.
In this way, she was more like her father, Draco Malfoy, than she could ever know.