I think this is a variation of what we in the US call the proverbial "royal 'WE'"; that is, perhaps her "our" refers to the common "our" -- namely, "British"?

I am no fan of monarchy -- and here in Sweden today we had to put up with yet another royalist birthday party (for the "crown princess") -- but there are deserved criticisms and undeserved ones. The "Queen" spoke well.