FirebaseUI/React email/password sign-in: Callback when email is already registered through Google sign-in

Question

I am using FirebaseUI React library for authentication using two provider options: Email/Password and Google. When signing in with email/password if user enters an email for which a user already exists (through google signin), how can I know about this in the UI? firebaseUI doesn't seem to have any callback or UI response to this. I only see this in the browser Network tab: POST: https://identitytoolkit.googleapis.com/v1/accounts:createAuthUri?key=AIzaSyC05EXy-1dPN6j6lJ8C2kGfLyDPINLIUIo Response:

{
"kind": "identitytoolkit#CreateAuthUriResponse",
"allProviders": [
"google.com"
],
"registered": true,
"sessionId": "ML2MvtkAofAwHzNn3VR1ps2Lt0E",
"signinMethods": [
"google.com"
]
}

Thanks in advance for any pointers.