At this age, she and her friend will fall asleep much quicker than the teens. Enjoy that while you can.
Cubette started sleeping over / having friends spend the night around this age. Only one friend fared poorly and wanted to go home cause she missed her parents. All others were mature enough. But, be prepared to walk her home if she gets too upset.
Same bed isn't a problem in my view, although a twin size would be a bit uncomfortable. I'd put some blankets or a sleeping bag next to the bed for sozlet and offer the bed to the guest. My kids understood that to be protocol even though they always all ended up on the floor.
Oh, and lay in some good snacks, drinks, maybe let it be a special night and order out for pizza. Get an appropriate movie they both like or maybe haven't seen yet. Don't read, take a hot bath or anything else that might make you sleepy before them. Have fun!