Hi
The correct way to unpair Apple Watch, including removing Activation Lock, is to unpair your watch using the Watch app, without first erasing your watch manually:
As you no longer have the Apple Watch in your possession, the following steps may help:
If you have not yet done so, remove the watch from Find My iPhone online:
- On a computer, in a web browser, go to: https://www.iCloud.com > sign in with your Apple ID.
- Open Find iPhone > select All Devices (at the top) > click your Apple Watch.
- Click Erase Apple Watch > Select Next until the device is erased.
- Click "X" next to your Apple Watch.
If you have not yet done so and if the option remains available, also unpair the watch from within the Watch app on your iPhone (even though the watch is not available):
- On your iPhone, in the Watch app, go to: My Watch (tab) > tap on the name of the watch (at the top) > tap on the "i" icon next to the watch > if the button is shown, tap on Unpair Apple Watch and follow the further instructions.
Having followed the previous steps, ask your sister to follow these:
On her iPhone: close the Watch app (double-press on the Home button, then swipe up on the Watch app preview).
Restart both her iPhone and watch, turning both off together, then restarting her iPhone first:
Re-try pairing and setting up the watch:
If the watch remains locked, either:
Accompany your sister and the watch to a Genius Bar appointment, taking along your original proof of purchase for the watch.
Arrange for your sister to return the watch, pair it to your iPhone again and then unpair it via the proper process (described above).
Or contact Apple Support and explain that you have been unable to remove Activation Lock from a watch that you have given away:
Note that Apple advises against disclosing your Apple ID credentials to anyone else, including family members.
More information:
About Activation Lock on your Apple Watch - Apple Support