SAS,
Naturally you are correct in your statement that the easy target is normally the one which is attacked, which is why so many expats now drive around in escorted armed convoys.
Many of the expats here have sent their loved ones out of the country, but it's not so easy when your loved one is a Nigerian. European and American embassies still make it very difficult even for a legally married partner to get a settlement or long-stay visa and many of those here who are married to Nigerian partners have no option but to step up their security as best they can and just brave it out in the hopes that things will get better
It's also entirely possible that the kidnappers asked for the father so that they could kidnap him as well as his daughter. By the way, he's not just a field hand, he's a consultant for Lonestar Drilling and part owner of a karaoke bar which, until a number of expatriates were kidnapped from there last year, was one of the most popular expatriate bars in Port Harcourt.