Ginny felt a bit of relief when she saw the windows go black, though that feeling of relief was soon replaced by another sudden feeling of tightness. "HNGH!" Ginny's back suddenly went rigid as she stood straight up, eyes widening as the skin around her chest seemed to ripple slightly, before ever so slowly her breasts began to inflate. "Nnnngh...." Ginny shivered as the sensation of her breasts slowly growing nearly overwhelmed her, it was certainly a pleasurable sensation. The skin stretched over her new breasts perfectly, leaving no marks or imperfections as the breasts continued to grow outwards, barely sagging down at all due to their incredible magical firmness.
About 60 seconds after the growth started, it finally stopped, Ginny Weasley now standing with a perfect set of DD breasts sitting proudly on her chest.