It sounds like she may have been planning to work for her cousin by caring for the cousin's children. Working on a visitor permit is a huge no-no, and will swiftly have you sent back if they find any evidence.
Something to be aware of is that most customs agencies now search electronic devices in your possession. They will insist on inspecting them and can turn you away if you refuse. This includes cell phones, computers, cameras, mp3 players, anything that can hold data. As most people have Facebook set up on their smart phones, they will take a look at your Facebook page too to see what you have been posting to friends about your trip. The also check messaging software and texts, and sometimes look for pirated material or pornography (child porn in particular obviously), even internet browsing history.
Personally I always traveled with a clean laptop, and a heavily encrypted external drive that looked like it was unformatted. The encrypted drive contained HIPPA protected client data, so there wasn't a chance in heck I was going to let some customs guard go through it. A lot of corporations also do the same when traveling, and keep backups on a secure file server for management to restore their computers after crossing the boarder.
Me I've never had much problems with the US boarder guards, generally they have all been really nice and helpful to me, but then I was a older white male holding a student visa. Canadian border guards, on the other hand tended to be more of a pain in the butt, though after multiple trips they generally tended to wave me through fairly quickly. I've had American friends tell me the exact opposite where the Canadian guards were very friendly, and the US guards very rude and short tempered. Maybe we just like being jerks to our own.
