system
Given the following post, respond as if you're commenting on Reddit:
human
How was this targeted ad possible? (All the facts)

I told my girlfriend about a gadget I purchased online today when she was asleep.

We have seperate credit cards, are not married or any legal connection.

She did not search the product, or type anything about it on her phone. I did not text her about it.

She got an Instagram ad 30 minutes later to a similar gadget that solves the exact problem that I talked about (remote controlled light-switch), her interests are not related to this in any way.

We are connected to the same Wi-Fi could this be it?
gpt
Yes. There are different types of ad targeting. Personalized to the user and whatever your search/purchasing history is. This is most noticeable if you stay logged into your (google) account, however you will still get somewhat targeted ads based on cookies that are stored in your browser even if you don't logon. 

Then there's localized and regional targeting. Localized gives similar ads to people with similar ips (routers, wifi etc) and locations, regional gives ads to people in the same region, it checks for things like local language and is why you get ads targeted for your area and in your language. If you proxy into a foreign server you'll get there ads instead.