Not a newbie but don't know how the donation works Example She is $500 hr/ $600 two girl show. Do I pay Each $300 or pay just one and let them split it?

You pay them both their hourly rate.

Some charge the full rate for each person (say $$$).  Other times there is a slight discount (perhaps $$$$$) for both.

I was quoted a single rate for the two women together, which is usually less than individual rates.  I put the total donation in one envelop and leave it up to them to split.  How would I know if it's an equal split or not?