Like most women, I think, she just wants the sizes to be standardised. Very frustrating for her to have three different sizes in her wardrobe even though the all have the same measurements.
It's not like that for us men.
Ha ha. I bought two new tops which are lovely, well made and fit a treat. And yes I do understand! The tops put a smile on my face and I was easier to live with (for the time being)! I have great trouble with jeans, and live in leggings and long tops. Oh to be a long slim thing again!!