Children with autism are taking in information just like people without autism do... But with autism the brain cannot control this influx of information causing it to over stimulate them... She is fine with you because your are just one person to focus on... When others arrive her brain is going crazy trying to take in all the extra sounds, sights, and smells. Find something she can focus on... Just one thing, like bouncing a ball, or coloring a picture, that will hopefully allow her to cut out other noise and simulation and help to keep her calm! Hope that helps!!
No maybe you can look to see if there are any clips on YouTube