yarp
I know exactly what you feel, it is super annoying indeed!
No matter how hard I tried, it is very difficult to destroy tracking altogether.
My girlfriend also has a Pixel 6(a) with GrapheneOS installed, even though her phone is full of commercial apps that try to track her sadly, I cannot force her to remove those, so I just have to live with it, but I am already glad she uses GrapheneOS, it helps quite a bit to prevent some more damage to her privacy and security.
If any third parties are connected to Meta, Meta can make a shadow profile of you, even of you never agreed with their terms and privacy policy.
Lets say my bank app has Facebook trackers in it, perhaps if I bought something in an antique shop my girlfriend might recieve ads on her Facebook about antiques because my bank decided to share my puchases or location info.
And even without a bank app, but just a digital purchase (like pinning in a store) might lead to me being added my puchase to my shadowprofile on Meta.
I once went to a webshop where I logged in to, and forgot to turn off tracking on that particular website, and my girlfriend knew exactly what I bought because she was recieving ads about it.
And even when I turned the tracking off on that website, I still have to trust them to actually have it disabled; I have very little control over that.
Also stores can use WiFi or BT tracking if MAC-randomization is not enabled. (It is also important to use the function "turn off WiFi/BT automatically")
And indeed, it is very possible that the thing you spoke about was being serached by your wife.
Also, there could be smart devices like speakers always listening in, the culprit does not neccesarily have to be her phone, it could be any of the "smart" products in the house.
Or perhaps another Meta product has tabs on her like WhatsApp?
Whatsapp is a proprietairy product made by Meta which is known to track. (Even though, I do not believe they spy on the messages themselves, merely on metadata of other phone usage and such. (Like some hardware features)
It may even track your location.
As a matter a fact, Meta can even see if people are in the same vehicle like a train, bus or car based on the motion sensors in the phones, if these match yours, it is assumed you are present in the same vehicle as the other Meta users, it might even get a cross-refererence to where others are going, so if they generally heading to a store, it is assumed by the algorithm you are doing that as well.
In short:
Lets say I go to the grocery store, and I mention that to my girlfriend, I also mention the brand of that store as well.
The following can happen;
-My girlfriend looks up some info about closure times of that particular store.
-My bank sees my puchases and shared it with third parties like Meta.
-WiFi tracking was enabled within the store and MAC-randomization was not enabled.
-WhatsApp tracked your location.
-You occupied the same vehicle as other shoppers.
-I probably miss a few more possibilities.
For me, all of these attempts feel like companies are weazling their way through, wether you consented to it or not, that is what I hate the most about them, I just don't want to be followed everywhere in favor of their ad-revenue, I wish I could just say "no", but society has devolved into these methods instead...
However, I don't believe it was her microphone that was listening in, it must've been something else altogether, it requires a little " out of the box thinking" in order to figure it out I'm affraid, I could never get a tab on it myself.
Please, correct me if I'm wrong on any of this, I only know so much about tracking, I am no expert.