These kinds of things might be just random. You see probably thousands of ads during the day, but most of them are not registered by your conscious mind. Only when there is a notable connection to something, your brain wakes up and you register the ad.

There's also the option that before bringing up something in conversation, your friend has made some related searches or reacted to a related ad. Facebook could then make the decision to show the ad to you based on your friend past behavior and the fact that you two had a conversation.

> These kinds of things might be just random. You see probably thousands of ads during the day, but most of them are not registered by your conscious mind. Only when there is a notable connection to something, your brain wakes up and you register the ad.

This is similar to the Cocktail Party Effect

https://en.wikipedia.org/wiki/Cocktail_party_effect

It's end-to-end-encrypted between the proprietary WhatsApp clients, but they might very well scan things inside of the WhatsApp client.