I understand that Mac was remotely erased through Erase a device in Find Devices on iCloud.com - Apple Support, but it was subsequently found and the erase request is no longer pending. If that's the case that Mac's content has definitely been erased. Now that it has been found, obviously she wants to use it, but she can no longer remember the passcode she used to lock it.
Have also tried removing it from find my but it wont let her
Please describe what happens when she tries.
If you find a previously lost Mac that was remotely erased, the only way to recover its use is to erase it (yes, again) and then remove it from Find My. Refer to Turn off Activation Lock on a device in Remove a device from Find Devices on iCloud.com - Apple Support: Step 2.
From what you describe Step 1 might no longer apply.
She will need to activate it again: Step 3.