Have her joining the network, then in the client list find her device. By clicking on her device you will be able to see the IP in use (which will change and it's pointless to block) and the MAC...

You should be able to block her by using the MAC address (which doesn't change and it is unique per device). But you will then need to block it/unblock it manually, there's no way to do so...

Hello everyone, I'd like to receive some clarification about my Deco P9 units. My current setup includes a standard VirginMedia WIFI modem/router, where the WiFi has been disabled and that has been...