I'm sorry I'm playing Devils advocate. I'm going off my experiences of Mums and Sons. Another funny story, when I got with DH and it was apparent that he would be staying where I lived once everything was done, MIL wasn't that nice. She quickly realised that if she behaved in a negative way, this would impact on things with her DS & GC.
So she did all she could, when they visit I work hard to organise a decent meal, show MIL pictures, get DS & DD to show off something they're proud off. Roughly once a month DH will go to his parents but it's not accessible for me, plus my condition can change quickly, so I'm better off at home.
MIL & FIL didn't rush to see DS or DD once they were born. I wasn't fussed, they could have come the day they were born if it was up to me. But they left it a few weeks. MIL uses her position to buy all the school clothes and outdoor clothes as she gets discount at a really nice shop, that is why our bills are low. She also contributes other things with FIL that help DH out. Like they take trips to Calais to buy certain things, we use French toilet rolls, washing liquid and washing powder, for that we are grateful.
My PIL also call several times a week. We've been together a long time, so very quickly they realised if they didn't get on board, despite their reservations, life would be a lot different in a negative way.
Whilst possible, I find it really hard to believe that there hasn't been an incident that provoked the situation. If it was solely DIL, putting her foot down, DS would text his Mum or contact her when DIL wasn't about.
It sounds like whatever happened impacted both of them and created the situation as it is now.
With my first marriage I wasn't hot on MIL but I adored FIL. My ex could do whatever he wanted, he had an active life, but I wasn't so keen, neither was FIL, being dragged to MIL hobby. On my only day off I wanted to sleep, not feign interest in something I knew very little about.
The funny part of that story was, MIL alienated herself, pretty much, against a whole village. People were tripping over themselves to tell me stuff about MIL.
So whilst I'd love to have empathy for OP, I do feel that crying as a response to DIL not engaging with her, was designed so the director felt sorry for his visitor, which would have impacted DIL. Who cries in the workplace, let alone an office that you are visiting. To me that is manipulative.
Imagine you saw someone whilst visiting another office, they didn't say hello, would you break down in tears in front of the director?