I don't know the current rules in your country or state, but common sense dictates that we cut down on visits.
We have been to see a family member who needed a bit of support and company, and driven right by others we would normally call in to on the way, in order to minimise visits.
So they may be going to see DiL's family, but don't want to add a visit - and maybe wanted to avoid a difficult conversation. I would add that if there is a 'reason' for visiting one family and not another, it may be confidential. I remember my MiL asking us to change plans because she had become ill, and she was frantic with worry that I would tell my mother the reason.
I agree with keeping the conversation generic - otherwise your GD may be given instructions to tell you nothing!
I think we have to be forgiving in these times, however hard it feels, and let some of these things go - hoping to mend fences / bridges next year. I hope you can do that.
I say the next in the hope of raising a smile, please don't think I am unsympathetic - we have English speaking posters from all around the world, but to most of us in the UK, 3 hours is a long journey! I always smile at my nieces in Oz 'popping' somewhere that's a 2-3 hour drive! But of course, here in the UK, that length of drive would include at least one traffic hold-up!
I hope you can enjoy your Xmas and making plans for next year.