That might be of interest, as she has had problems with the inverter before so reporting what is being generated / fed to the grid is more fundamental than if the AC is connected.If the wifi can be made reliable you could wire in a Shelly EM and clamp the relevant circuit to have a nice history of the consumption too. It works via the cloud so requires registration for remote access, but with no monthly fees.
Having said that, most folk are not going to check often so by time they look it could have been weeks of outage so really something simple like a SMS alert would be ideal. If it can be made cheap enough!