FWIW, I have been collecting on my ex-wife's SS account for the past few years as I let my own SS benefit increase until I am 70. I never bothered to tell her since it has no effect on her SS payments. She remarried long ago, so she could not collect on mine even if she had considered it (which I doubt she has).
From time to time when she does something I don't like (usually involving letting down our children or grandchildren ) I get upset and think I should 'rub it in'. But, instead, I realize it is a petty feeling, it won't make 2¢ worth of difference, and it certainly won't change her future decisions. Then I go outside and play with my grandchild and realize how good my life is. In fact, thanks to her reneging on a babysitting commitment she made, I will be playing silly games with a grandchild all of Thanksgiving week. Bring on the fun!!!