I think one of the main essences of BLW is they eat what they want so if you put the half a roast potato and 2 bits of asparagus on her tray and they get eaten, put some more on and let her carry on.
I think as time goes on you will start to learn how much she will usually eat and judge well what to put in front of her.
I think as time goes on you will start to learn how much she will usually eat and judge well what to put in front of her.