>>I talked to her about, for example, Jordan Peterson, and her phone starts blowing up with Jordan Peterson on Instagram.
And why did you talk to her about Jordan Peterson? Is it perhaps because you read an article about Jordan Peterson earlier? If so, I assume you both share the same IP at home - so she starts seeing things you viewed or browsed. Facebook owns Instagram too, so if you look at something on Instagram it's not that wild that your partner's Instagram starts showing her things that interest you - it's just association.
>>If you have "OK Google" or whatever it is turned on, it is indeed listening to you.
Sure, and that's what I meant in the first paragraph - no one has been able to prove that this feature is sending your voice to Google/apple/Amazon servers unless you trigger the key word. Recording and sending voice would create some trace and no one has been able to prove this exist. That's not me saying it doesn't exist, just that for what is supposedly wide spread phenomenon, we have no proof it's actually happening other than anecdotal stories which can be easily explained by other means.