They build up a database of your connections and locations. As they already know you both live in the same house with the same surname, your relative distance on a single given day is irrelevant. If the wife's googled it the it's highly likely you'll be targeted with similar advertising to promote a purchase. Alexa on the other hand, that thing is always listening and you can see some of what it's recorded on your Amazon account. I've honestly just given in with it all, it's not like I talk about anything important (nappies and paw patrol mainly) at home anyway.