Setup MacBook with wrong email address, now MacBook is activation locked

You need to unlock it using the same Apple Account credentials that you used to lock it.

I don't think you'll be allowed to change her Apple Account e-mail address to the one that you did use. Why? That e-mail address is probably associated with a different Apple Account (possibly one you created) already.

Since you have no receipt, I doubt if Apple will help you to remove the Activation Lock.

Your employer is considered the owner of that Mac. So if all other attempts to unlocking fail, then you will need to have your employer (or former employer) get it unlocked for you since only they can prove they are the legitimate owners (in Apple's eyes). Otherwise that laptop will be just a brick.

The Locked to Owner screen should show you a partial email address to the user it is locked to, and that is the one that will need to be entered to remove the lock. If that email address was determined to be one you used previously, then you can use Account Recovery to gain access to the account if you no longer remember the password that was used.

How to use account recovery when you can’t reset your Apple Account password - Apple Support

There is no reverse lookup to find the email address used, but Apple provides a couple of methods to help you find it if it was yours.

If you forgot your Apple Account primary email address or phone number - Apple Support

The email displayed has to be an email used for an Apple Account, there is no other way the Activation Lock can be used without one. You can certainly use an email address with a personal domain as an Apple Account, but you have to previously create that Apple Account using the email address where there will be a verification email sent to it, followed by creating a password for that Apple Account.

Entering that email address by accident when setting up the device will not automatically create an Apple Account for that email address.

CelticDaddio wrote:

So if the email displayed one the activation lock screen is “herusername@personaldomain.com” is that what MacBook is locked to?

If that e-mail address is associated with the Apple Account to which the MacBook is locked, that e-mail address and the password for the corresponding Apple Account are what the MacBook is asking for.

Presumably you had to provide this password when you originally set up the MacBook. If you had attempted to associate it with a complete stranger's Apple Account (by mistake), but had not known the correct password, I believe the attempt at doing the association would have failed, preventing you from "giving away" the MacBook, by mistake, to the stranger.

CelticDaddio wrote:

My employer is not the owner of the MacBook. It was a gift to me, not provider for my use.

If your employer ordered & paid Apple or an Apple reseller (or processed it on your behalf), then they are considered to be the first owner and the only owner which Apple knows or cares about. They would be the only ones with the acceptable proof of purchase which Apple would accept to unlock a device.

Unfortunately receiving a secondhand Apple device has some major downsides unless it was an official Apple refurbished device. This is one of those major downsides if you cannot remove the activation lock through normal means of an end user. As long as you are on good terms with your employer, then they should be willing to assist you with having Apple unlock the device if other methods are unsuccessful.

CelticDaddio wrote:

My employer is not the owner of the MacBook. It was a gift to me, not provider for my use.

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