Some extra information from Sofie at the Glittering Royals message Board:
"This must bring special feelings to her (Mathilde) since her sister Marie-Alix and her grandmother died in a terrible traffic crash. that's one of the main reasons why they were there today. You can see on a few pictures that Mathilde is trying very hard not to cry.
You can even see Crown Prince Philippe looking at his wife to see how she's cooping.
As the eldest of the d'Udekem d'Acoz-children she saw very closely what the death of her sister did to her parents. For her mother, it was just that bit harder as she also lost her own mother in the same crash.
Crown prince Philippe went to their funeral, so it's known that Philippe and Mathilde were allready close back then. It was said by the family priest that helped the family through it all as a background reportage of the event in the Belgian television programme Royalty. He even told that every song, every prayer, every piece of text for the funeral had been selected by Mathilde personally.
A representative of the organisation also told that there has been a lot of interest for the organisation from both Mathilde as Philippe, they have had informal conversations before. He also stressed out that the presence of Mathilde and Philippe to the "memorial service" meant a lot to the parents that had lost a child in an accident. "