Sign out of Apple ID Remotely

As you have used the Find My remote erase, as soon as the iPad is powered-on and connected to WiFi (or Cellular if the iPad is a Cellular model with an as active Cellular connection), the erase command will be delivered and executed.

When the command is received, the iPad will instantly erase the iPad’s Secure Enclave - this being the iPad’s security chip within which all the cryptographic keys are stored. The iPad uses an encrypted file-system - and without access to the [now wiped] crypto-keys - cannot access any locally stored data. The device is also immediately locked-out.

Until the iPad is restored from this condition, it will be completely unusable. When [if] restored, the iPad will be Activation Locked - and will remain useless until such time as the owner of the AppleID that last successfully activated the iPad (presumably you) releases the Activation Lock.

The Activation Lock can only be satisfied/removed by the owner of the AppleID that currently secures the device signs-in with the correct AppleID. To do so, assuming the iPad is not accessible to you, follow the process outlined here:

What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support

If you no longer have your iPhone or iPad



If the steps above weren't completed and you no longer have your device, use these steps:

1. Ask the new owner to erase all content and settings using the above steps.
2. If you're using iCloud and Find My [device] on the device, sign in to iCloud.com/find or the Find My app on another device, select the device, and click Erase. After the device has been erased, click Remove from Account.
3. If you can't follow either of the above steps, change your Apple ID password. This won't remove personal information that's stored on your old device, but it prevents the new owner from deleting your information from iCloud.
4. If you're switching to a non-Apple phone, deregister iMessage. 
5. If you're using Apple Pay, you can remove your credit or debit cards at iCloud.com. Choose Account Settings to see which devices are using Apple Pay, then click the device. Next to Apple Pay, click Remove.
6. Remove your old device from your list of trusted devices.
7. If you purchased an AppleCare plan for your device, cancel your AppleCare plan.

The device will be erased and she will have no access to your messages. The only problem may be that the iPad is now locked to your Apple ID and she will not be able to use it. You can remove the Activation Lock remotely by following this support article:

How to remove Activation Lock - Apple Support

To view devices that are signed into your Apple ID, you can do that here and also remove them. If the device is erased, then it should no longer appear on this list.

Check your Apple ID device list to find where you're signed in - Apple Support