Can my client change the privacy of his Quick Books so his employee can't see the Dashboard summary on her log in?

Yes, your client can easily change the access rights of their employees, 9130 3486 4601 6776.

Currently, the Dashboard details can only be seen by users with the following access rights:

• Master admin
• Company admin
• Accounting firms
• Standard user with All access

Your client's employees must only have the following access rights so they can't see the Dashboard information:

• Standard user with Limited access to customers and sales
• Standard user with Limited access to suppliers and purchases
• Standard user with None as the access rights.
• Reports only
• Time tracking only
• Take payments only

Here are the links that you can use for reference: 

• What different types of users can I add to my company?
• User types and user permissions in QuickBooks Online

Let us know how this goes so we can further assist you in managing your client's users.