so what happens when she sees ads for mail order brides?

and yes, all of the ads shown to you are based on a combination of the content of the page you're on and Google's knowledge of your browsing/shopping/online history. As someone with lots of knowledge on how this stuff works, it's actually really scary but incredibly cool.

For advertisers, it's becoming possible to tailor ad content to users based on their past behaviour on the advertiser's site. There's a feature called retargeting where, for example, if you are looking at a computer part on Newegg, that part will show up in a Newegg ad on the EE forums, reminding you about it and offering other complementary parts. It's a way to re-engage customers that have fallen out of your purchase funnel before converting.