the OP's an IxFP, of course she doesn't want to hurt the INFJ's feelings, and that is a noble goal. Possibly a futile one, but noble nonetheless. If you (I'm just gonna tell you what to do, if you're not the liked one, but are in fact doing this on behalf of a friend or whatever, just consider it directed at them) want to get really crafty you could try running a distraction, finding someone you think they might be attracted to and siccing them on this INFJ, so they've got someone else to obsess over. That plan has an extremely high chance of failing and/or blowing up, though. So don't do that unless you're positive it will work.
Other than that... yeah, as Costrin said. Distance is probably your best bet. Although this does have a chance of "absence makes the heart grow fonder" syndrome, where the limited interaction will cause them to obsess more and inject those infrequent meetings with even more significance.
I you want a more direct, more likely to work method that will probably hurt their feelings, is to just up and say "This isn't going to happen, NO MATTER WHAT YOU DO. And if you don't accept that we really can't hang out, it's just gonna be awkward." However, I have found that even THAT can fail, especially if the INFJ likes to drink.
My friend's been chased off and on for nigh on a year now by an INFJ with a similar tendency. We still haven't been able to shake her. So good luck.