The fact she was granted a visa does not obligate you to anything.
Hypothetically a manipulative person would still come here, despite your objection to continuing the relationship, using a combination of guilt-tripping and the occasional sop of pretended affection being thrown your way.
Hypothetically the target falls for both ploys, feeling guilty when they were the target of cynnical manipulation from day 1 and getting all giddy over the slightest morsel of fake affection. So he allows her to live with him.
Hypothetically the target marries, knowing it is wrong but feeling trapped and desperately hoping for a miracle - maybe she will love me in the end; I will prove I was a gentleman. I will suffer like Jesus on the cross.
Hypothetically the manipulator divorces the target after months of more misery than he has experienced in his lifetime. Hypothetically she is granted the green card on her own.
Hypothetically there are 2.7 million genuine, loving, wonderful Filipinas who would die to take her place and make this man the King of the World. But instead of doing justice and bestowing upon the deserving a wonderful life of family and security this man rewards the scheming evil witch. Thus the strategy of evil is perpetuated by virtue of its success and the strategy of honest and sincere effort is punished.
In the end then what this hypothetical man does is teach others that dishonesty, cheating, and evil intentions are the key to successful immigration.
His excuse will be that his intentions were good.