Hello Carolee,
Thanks for using our plugins and welcome to the forums!
Great question. Currently, if you want your client to access the attendee list / data without your interaction, then the only way to do that is via logging in to the WordPress site and checking there.
With your interaction, there is the possibility to email them the attendee list from the backend, when you go to the Attendees page of an event.
Other options would require custom development and with those some kind of authorization / login would be needed.
Does this help?
Cheers,
Andras