As has been said, this was NOT her birthday- it was her birthday party. I know that's what you guys meant, but I don't think everyone's keeping it in mind. Yes, this party was big- but I think if Beatrice REALLY wanted them there, they would have gone. And looking in saying, 'This was a great big party with so many people' does not mean it was her family party (which we know it wasn't). For my next big birthday, if I have a big 'gala' that I start planning over half a year in advance (which is a possibility), I can tell you that I won't care if my cousins or grandparents come, and we just don't know enough to say, 'Well, Beatrice does!' I also think people are turning this into a Fergie vs Philip thing for no reason. We do not know why he didn't go. Just because Fergie was there, that does not mean it is the reason.
Also, which papers said the Queen insisted it would be held at Windsor? I have seen it written that she offered to have it there (although I don't have the sources pulled up at the moment) and am curious to see which papers are saying she 'insisted' so. (Also, keep in mind, the size and the security as well as logistics may have been what put it at Windsor. I think people are reading way, way more into this than can be reasonably proven.)
Edited to add: I am not saying that I think my opinions are necessarily correct or what is being said is necessarily incorrect; just that there is not enough to base it on (because this type of event in Beatrice's life is unprecedented I don't count family relations at base events as proof).