My sister and my Husband Drinking Fun Time?

[SomedaysDiamonds]

My Sister just admitted to me, that she and my now ex-husband, spent a night together in a motel, "just drinking", nothing else happened.....
Well...I can be naive sometimes, but why would she tell me this, now?
This happened 40years ago, when I was still married to him.
First of all, I can't believe the gall in her telling me this, as my sister, let alone, a friend. I am just writing this to vent, I guess. Because she is old now, and I don't want to say anything to her. I just want to let this go, but it is just wierd and sick to me. Strange to think about.

Responses welcome. Good day