I think it's possible to have a good close relationship with an INTP, but because of the clash of cognitive processes, it would take conscious effort from both people make it a good relationship. You've got two people whose favorite functiosn are in the others' shadow:
INTP: Ti, Ne, Si, Fe (shadow: Te, Ni, Se, Fi)
ISFP: Fi, Se, Ni, Te (shadow: Fe, Si, Ne, Ti)
No complimentary functions there, and the two favorite functions of each are least favorite in the other person's shadow. So there would have to be a lot of conscious desire to learn from the other and respect the other, without anyone needing to be "right" about anything.