Understandable decision of Shigure

Her displacement's already gone up...

Please give up and show her, Yamashiro. She'll turn into a heavy cruiser at this rate.

A slow armored cruiser. She engines can't keep up with that hull form.

At least she has a sister who can teach her how to shoot like a heavy cruiser.

Chubby Shigure is fine too.

I feel like I'm missing an obvious joke here. How is Shigure wanting to see Yamashiro's new outfit related to eating and drinking a lot?

You get a random card with certain items at Nakau (as shown in the notes); Shigure bought up large to ensure that she got the Yamashiro card.