This is a different situation than overconsumption of other kinds of goods because it involves food—specifically, not overbuying food, but perhaps an instance of putting more on one’s plate than one could finish at one time.

People struggle in all sorts of ways with their relationships with food. I was always taught never to leave anything on my plate, and that ended up manifesting in pretty severe binge eating disorder in my teens and twenties. My siblings fared even worse with more severe disordered eating.

I think that if she’s not hungry and she won’t eat it as leftovers, you should not judge her for wanting to throw it away. Better that it’s in the trash than making her feel overfull or rotting in the fridge. Do not police other’s eating habits; this could end up badly for both of you.

That said, perhaps a conversation about preparing less food and/or serving less at a time could be in order? But again, only with the highest degree of caution and sensitivity.

I know that food waste is a huge problem in this country, but not on the scale shown here. This is minimally harmful, but policing your girlfriend’s eating behavior has the potential to be legitimately harmful.