[Sidney_Ivan]

I would hope that most family members would be understanding if you just explain that you are trying to stick to her sleep schedule so that she doesn't get overly exhausted/stimulated on such a big day. For those who don't, you could always put a cute sign on her bedroom door that says something like, "Our birthday girl is getting her beauty winks- please do not disturb." It might make those tempted relatives to think twice.

[GCS]

Its hard to put your child to bed when there are guests over and they are having a good time. I am going to swim upstream here and just say what I would do.

I would start telling her at 7 that it will be time for bed soon. At 7:30 I would let her know she's getting to stay up a little late because it is her special day but that means no fussing at bedtime, and at 8 I would put her down.
I'm pretty strict about letting my kids have something but letting them know what that means - ie - you get this extra time up because its a special day but that means a no-fuss bedtime. And both my kids are pretty good at obeying this and hearing me talk to my children about how it is bedtime soon helps guests to get that the party is over.

Good luck!