Ttyjukl

Towards the end of Order of the Phoenix, after Umbridge has been carried away by the Centaurs, and when they have to get away from Umbridge's Inquisitorial Squad, Ginny overpowers Malfoy in Umbridge's office.

“How did you get away?” asked Harry in amazement, taking his wand
from Ron. “Couple of Stunners, a Disarming Charm, Neville brought off
a really nice little Impediment Jinx,” said Ron airily, now handing
back Hermione's wand, too. “But Ginny was best, she got Malfoy – Bat
Bogey Hex – it was superb, his whole face was covered in the great
flapping things.”

Shouldn't Ginny own Malfoy's wand then? Harry should have had to disarm Ginny to get Malfoy's wand in the last book. So how does this work? Do they need to claim the wand as well, besides overpowering the owner, as Harry did in the final book? Then why does the Elder Wand belong to Malfoy and then to Harry, as non of them actually claimed the wand after overpowering their respective owners?

It's only the Elder Wand that changes allegiance when its master is defeated. That fight between Ginny and Malfoy took place before Malfoy disarmed Dumbledore and became the new master of the Elder Wand. Fights he lost before that are not relevant to the mastery of the Elder Wand.

In Deathly Hallows chapter 24, we're told

“Hawthorn and unicorn hair. Ten inches precisely. Reasonably springy. This was the wand of Draco Malfoy.”

According to this answer unicorn hair wands are very loyal and don't change allegiance easily. Since Ginny didn't keep Malfoy's wand, she never gained its allegiance.

I don't agree that it's only the elder wand that will change allegence.

With wand lore Olivander states that wands can change allegence, he doesn't specifically mention the elder wand in that statement.

So, does Ginny own Malfoys wand ? I'd say no, purely because she just cast the 'bat bogey hex', this doesn't mean she disarmed him.

Also, there has to be a wand lore limit to 'wand changes allegence after defeat/disarm' otherwise the members of Dumbledores army, when practicing in the room of requirement would have been changing wands left right and centre !

Maybe Ginny would have had to take Malfoy's wand physically in order to get it to change allegiance?

I think it's a plot inconsistency. Ginny overpowered Malfoy in a combat situation, so surely, the wand allegiance would change, no? Maybe JK Rowling forgot to use her own rules here.

On the other hand, maybe you have to use Expelliarmus, the spell to make a wand fly out of someone's hand, or some other spell to very specifically knock someone out of the way - although she used Bat Bogey Hex, so that should do it. It's very odd she doesnt just go grab the wand, because if nothing else surely the kids could use an extra weapon at the dept of myst when they go to fight? Even if it had not switched allegiance and she wouldn't have been able to do good spells with it, you can still use a wand to stab an eye (excuse the grossness please!).

Perhaps it did.

Harry never had any interaction with the Elder Wand (prior to the final battle with Voldemort). He didn’t disarm it from Dumbledore, nor did he disarm it from Malfoy. All he did was disarm Malfoy’s regular wand.

In order for Harry to have the Elder Wand’s allegiance, then, we have to assume that when one wizard disarms another he gains the allegiance of not only the wand he disarmed but all wands currently under the allegiance of that wizard. By disarming Malfoy Harry thus gained the allegiance of all of Malfoy’s wands, one of which was the Elder Wand.

Now let’s consider Ginny. If we assume that the Bat-Bogey Hex counts as defeating an opponent then that would mean that Ginny gained the allegiance of all of Malfoy’s wands at that time. Then a year later Malfoy defeated Dumbledore and acquired the allegiance of all of Dumbledore’s wands, including the Elder Wand.

Almost a year after that Harry defeated Malfoy. That means that he then acquired the allegiance of all wands whose allegiance was to Malfoy. That would include the Elder Wand but it would not include Malfoy’s original wand. Since Harry never defeated Ginny, that wand still owed its allegiance to her (or to anyone who may have defeated Ginny in the interim).

The conclusion of all this would be that Harry had the allegiance of the Elder Wand without ever interacting with it, but he did not have the allegiance of Malfoy’s wand despite disarming it from him.