To change their email address, you'll have to edit it from their vendor's profile, Jennifer.
If you accidentally tick the Email this contractor checkbox while creating your contractor's profile, you won't be able to edit their email address in the Contractors section. If this option is selected, you will need to wait for your contractor to fill out their information before making any changes.

Since you wanted to change it, please follow the steps below to do it successfully:
- Open your QuickBooks Online account.
- Go to the Expense tab, then select Vendor.
- Find and open your contractor's profile.
- Once done, click the Edit button.
- On the Name and contact section, head to the Email field and edit it.
- Once done, click Save.

I'm including this article for guidance on preparing tax forms for contractors using QuickBooks: Create and file 1099s.
Feel free to comment down if you have further questions about this.