The first thing she has to do is to create a User password on her computer and ensure that all her email accounts are password protected, also she should ensure that passwords have numbers or special characters to make it difficult for others to guess.
Then she can create a "GUEST ACCOUNT" on her computer, guest account lets other people use her computer without being able to change PC settings, install apps or access her private files and documents.
Secondly, she can Set Permissions on Files or Folders, what this means is that she can password-protect important files, documents or folders on her computer. By editing the permissions settings of files and folders, she can grant or deny access to specific users, such as a guest user mentioned above.
Thirdly she needs to lock her PC when going for lunch or a break, on a Windows 10 PC, simply hit the Windows key and the L key on your keyboard, and that locks it from unwanted visitors.
She can also encrypt files and folders on a Windows PC by using the Encrypting File System. This is quite easy, just right-click on the folder or file in question, click on Properties, and then click Advanced, you will find a box that says "encrypt contents to secure data", check the box and click ok, done.