Any reason/excuse a stray cat could believably have an accessory?

So, I need help setting up and disguising a late-book twist I'm planning in my urban fantasy story. Basically, a set of significant secondary main characters in the book is a group of adventurous 8th-graders (who call themselves the Mad Dogs because their first initials, Merry, Adam, Daisy, Oliver and Gordon, spell out MADOG) who find out about the supernatural world the proper main characters are dealing with, and try to solve mysteries and do their part to protect the town on their own. Joining them is their sort of de-facto mascot, Madcat, a stray cat who seems to have taken a serious liking to them and follows them around on just about all of their adventures.

...In reality, it turns out that this "cat" is actually Daisy's Auntie Cammy, true identity Princess Chamomile Amberwing Karnstein, a powerful vampire with shapeshifting powers. She's been following them around on their adventures to keep an eye on Daisy and her friends, and make sure that if anything truly awful happens, she'll be there to bail them out if necessary. However, she's also in hiding from the powerful vampire royal family she's estranged herself from, so she wears, at all times, in both human and cat form, a piece of enchanted jewelry that makes it impossible for magical creatures to pick up her scent (which would otherwise be an instant giveaway that she's a monster to a great many people she wouldn't want to know).

But there's a big problem with this that recently occurred to me: she's pretending to be a stray cat. Strays don't wear collars, and in fact don't tend to wear anything, so this piece of enchanted jewelry would stick out like a sore thumb basically no matter where she wore it and raise a mountain of questions about who put it on her and why, questions that my very inquisitive kid heroes would be in no mood to leave alone.

She can't pretend to be Daisy's actual cat because "Auntie Cammy" lives with Daisy and her adoptive mother, and Daisy would inevitably notice that she never sees "Auntie Cammy" and Madcat at the same time.

She can't pretend to be someone else's cat because "Auntie Cammy" could not possibly hope to spend enough of her time pretending to be some other family's cat, even if they did let her wander around on her own most of the time, and surely the kids would wonder whose cat they're palling around with if she shows clear signs of having an owner, and if they fail to find any signs that said owners exist, that would be something these kids would definitely be inconveniently intrigued by.

I have an incredibly half-baked idea revolving around Daisy's mom (who knows who her "sister" really is) saying they can't keep Madcat because Auntie Cammy is allergic, but they can make a little shelter for her and leave food out for her, and maybe Daisy's mom likes tying a bright yellow bandana to Madcat's neck all the time that just so conveniently conceals the magic jewelry she's wearing underneath... but that feels so desperately contrived that I thought I'd ask around here to see if I'm missing a way simpler solution.

 

I think your answer lies in that little "Don't tend to." And yet this stray (so they assume) has a collar. Most strays don't. Maybe they reason that a cat could conceivably decide to leave its owner, and of course has no way to take its collar off. Maybe they leave it outside for many days (giving it food and water of course) to allow it to go back home if it wants, but it stays with them. So they decide it must have belonged to someone and for whatever reason doesn't want to go back to them. It happens. My neighbor's cat is now an outside cat. He hangs around in the area and they put food out on the porch for him, but he won't go in their house or anyone else's. I took him into my house twice but all he did was wander around forlornly yowling until I let him back out. He just became an outdoor cat.

 

Cats run away from their owners all the time.
My coworkers cat went missing for 2 months and was found on the other side of the state.

The cat/aunt could pretend to be a run away

 

So, I've been thinking about this and taking in the advice I got, and I think I have a solution:

Madcat is technically Daisy's cat. They adopted her, she has a collar with her name on it (and that has the jewel hidden in it). But she's an extremely independent and outdoorsy cat, so all this really amounts to is providing her a little space in the backyard with some food and a small roof. Madcat never actually goes in the house, or even spends much time at all near the house, which is just as well, because Auntie Cammy is allergic to cats.

Does anyone see any problems with this cover story?