It could also be that her Facebook profile was public and she posted public status updates (default FB privacy setting) about what she plans to do in the US. No

It could also be that her Facebook profile was public and she posted public status updates (default FB privacy setting) about what she plans to do in the US. No PRISM necessary for that, just a FB account. Just try a search on FB for a random name and open a couple of profiles. It is baffling how much personal information is publicly available.