Whose fence is it anyway

[Paul Zofsak]

I just purchased a property in Spring Texas.  As my GC was getting ready to put up a fence between mine and the neighbors house, the neighbor said it was her fence and her nephew was going to put it up.  There was no fence two months ago when I viewed the property for the first time and I have no reason to believe it will get done in time for me to rent my property; hopefully in less than one week.  What remains of the old fence is on my side of the property line but the new fence posts that her nephew put in are dead center on the property line.  So, my question is who is responsible for the fence, who pays for it, is it a shared expense or is just whomever puts the fence up on their property?