I am not nigerian but lived in 4 continents. the simple answer is mutual, the christian girls see a brand of innocense in the muslim guy, mainly because muslim come from a sober lifestyle, and the muslim guy likes the christian girl because she comes usually from a more worldly society and can show him the world and speak the language of the world. other christian girls will find most muslim guys either naive, stupid or just uncomfortable with the religion. other muslim guys dont in the first place date, and will find most christian girls too promiscous.

A christian girl knows from her own brothers and ex boyfriends a certain brash nature to sin lie or cheat and she may see a controlable man, trustable man in a muslim becuase usually he isalready tamed by his religion, hes less likely to cheat or look at other women and more likely to want marriage and father a child.

in many societies where christians and muslims live together you will see christian women turning to muslim men because christian guys are not ready to buckle down to one women,, especially if eductaed and have ok income. they want to play way in to the late thirties fourties.
im not trying to bias im just stating my observation including personal experience, (I am muslim)
I met christian girls where we had extreme chemistry but I didnot want to give it achance because I know I want marriage and kids and it wont work unless she converts and she alienates from here family,