My nine year old sister just got home from getting her galbladder removed.
They had to fill her body with gas, and she is having some pain.
Also her stomach hurts.

I was wondering if anyone knew any way to cheer her up.

Watch some movies together, get some coloring books, I don't know what kind of hobbies you're into but maybe teach her something new. Or learn something together. Go into a craft store and see what catches your eye

Good idea. We are watching Office Space right now :P
I just hate seeing her sad and in pain :(

yeah, it's hard to see someone you love hurting. She'll get better though, just be there for her while she's down. I'm sure she appreciates it. =)