To me, it seems a little late if that's when the party's actually starting. But if it had started sooner, but some people would only be heading there at 11, that wouldn't seem odd. I'm also wondering why she wouldn't invite you along.
“This planet has - or rather had - a problem, which was this: most of the people living on it were unhappy for pretty much of the time. Many solutions were suggested for this problem, but most of these were largely concerned with the movement of small green pieces of paper, which was odd because on the whole it wasn't the small green pieces of paper that were unhappy.” ― Douglas Adams, The Hitchhiker's Guide to the Galaxy