Hong Kong Power Outlets
What's the cord pinpointed with the red arrow called?
It's an AC Power Cord - either an IEC 320 C7 (non-polarized) or an IEC 320 C7 (polarized) - cannot be sure from your image.
Does she need to bring it? Does she simply attach a plug adapter to the end of the red-arrowed cord?
She can either bring it and buy an appropriate adapter (Canada to UK Plug Adapter), or just buy a new cable with the correct plug from any computer shop.
See IEC - World Plugs for more information on plugs in different countries.
Must she buy another cord like it, but for 220V?
No. Her adapter is already rated for 100-240V. Hong Hong is 220V.
Electricity and Voltage | Hong Kong Tourism Board:
The standard electrical voltage in Hong Kong is 220 volts AC, 50Hz.
The majority of electrical outlets in Hong Kong take a three-pronged UK-style plug. You can buy an inexpensive adapter for your electrical equipment at most convenience stores.