Do I need to crack this out again?
Height: 160 cm
Weight: 46 kg
Breast: 79 cm
Waist: 58 cm
Hip: 80 cm
If we translate those numbers, while Saten is no meronpan, she's still a sizable upper B/lower C cup. Furthermore, the shower scene is viewed upwards from below, which makes the breasts look bigger than usual.
It's really in line with my theory that animations tend to have more realistic body proportions than their original art when actual numbers are revealed.