A Teshuva Dilemma for the Last Yom Teshuva of the Season

Today is Hoshana Rabba - the last day of sukkot.  The highlight of the day is the ancient custom, now universally accepted (I think), to complete seven hakafot during hoshanot, as opposed to the single rotation around the Torah that we do on the first 6 days (or five of them, at least), and then recite an extended tefilla on a set of five aravot, and then beat them against the ground.  Warning: davening is very long tomorrow.  Beyond that, there are other minhagim - many congregations read the entire sefer Devarim tonight, many men go to the mikva tomorrow, the chazan wars a kittel and uses the nusach of the Yamim Noraim - many of which reflect the kabbalistic tradition that today is the final sealing of our judgement that began on Rosh Hashana.  Therefore, if you haven't yet said either Tashlich or Kaparot, tomorrow is the final deadline.

In that spirit, recently someone asked me a question that reminded me of a favorite machloket of mine.  She had accidentally been motzi shem ra about someone (said something bad about her to others, that turned out to be untrue).  How, she asked, is she to do teshuva?  Should she tell her victim, currently blissfully ignorant of the entire episode, what she did in order to ask her forgiveness?

The roots of the answer to this question go back at least a hundred years.  When the Chofetz Chaim (the  person) first published the Chofetz Chaim (the sefer on the laws of Lashon Hara), he tried to get a haskama from Rav Yisroel Salanter.  Rav Salanter refused, because in the sefer, it ruled that in our case, the offender may / must tell his victim what he did, and beg forgiveness.  Chas v'shalom said Rav Salanter, just becase you need mechilla doesn't give you the right to cause more pain from the target of your words.

I had always thought that in this machloket, the Chofetz Chaim was the lenient one, and that according to Rav Yisroel Salanter, the sinner is stuck with his aveira, prohibited from seeking the mechilla he needs to complete his teshuva (though both would agree that you could always seek the weaker, generic form of mechilla- asking for forgiveness for all offenses without specifying anything in particular).  In the Rosh Hashana To Go, Rabbi Josh Flug cites this machloket, but he assumes that according to Rav Salanter, you would be able to complete your teshuva without receiving forgiveness from the victim.  It works well with his thesis (עיין שם), but I'm not sure why he makes that assumption.

The person who asked the question was of course fascinated by my discourse, but then stumped me when she asked what she should do practically.  I promised to find out, and I'll let you all know when I do.