Wow Elphie, I guess you're lucky with your sleep schedule. You don't have to deal with being exhausted from getting up earlier than you're used to...well, at least to the degree I have to sometimes.
You could always do games. It totally depends on her age, but let's see...there's treasure hunt, where you pick a random thing to be treasure, and then write a bunch of clues and hide them throughout the house. Like...clue #2 is in something wet could be a sink, and then in the sink is a paper that says clue #3 is somewhere you sleep, etc until one says the treasure is, and then the person finds the treasure and wins. I used to love that game, but that's probably for if your sister's on the younger side.
If it's hot, you could always play tag with your hose. That's fun.
I very randomly decided I miss my slip 'n slide.
Or, if all else fails, get her started on a computer/internet game...snood, spider solitaire, diamond mind, text twist, etc. Those things are soo addicting, she can waste hours on there.
"If there was a Mount Rushmore for Broadway scores, "West Side Story" would be front and center. It snaps, it crackles it pops! It surges with a roar, its energy and sheer life undiminished by the years" - NYPost reviewer Elisabeth Vincentelli