well Face ID is Face ID.. whether it's for unlocking your phone or for an app, same thing.
Not likely something that would be classified as a 'bug'.
Does your daughter know your iPhone passcode? If she does and she uses it, it's like teaching your iPhone an alternate appearance.
It's also possible that you two look similar enough that this will continue to be a problem, in which case, you could turn off iPhone unlocking with Face ID and just use a passcode.
My suggestion would be to reset Face ID by going to Settings > Face ID & Passcode > Reset Face ID
Set it up again and make sure you are the only one present.
(resetting Face ID will likely require you to sign into some of your apps again, so make sure you know all your passcodes/passwords)
If she knows your iPhone passcode, or you suspect she might know your passcode, change that too. Same Settings area, select Change Passcode.
If she is still able to unlock the phone with Face ID after it's been retaught, then up top in this Settings area, toggle off the switch for iPhone Unlock. That would at least prevent her from getting into the phone.
About Face ID advanced technology - Apple Support