What type of ball is this girl holding and why isn't the other girl holding a ball?

What type of ball is this girl holding and why isnt the other girl holding a ball?
I've seen a ball like this before but never knew what they were called. Does anybody have an idea what they are called?

At first, I thought it maybe was a crystal ball but that doesn't make since as that's more associated with evil and I can't see them being into witchcraft or whatever.

Please tell me what type of ball this is!
Updates:
2 mo
Please change this to Arts and Entertainment. No idea why they placed it in sexuality.
What type of ball is this girl holding and why isn't the other girl holding a ball?
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