Why is Kitty so ashamed of herself after allowing Charlie to seduce her in Chapter 76?

Kitty is completely disgusted with herself after she allows Charlie to seduce her in his home. This is in part because she no longer loves him and merely gives into his kisses due to self-pity. However, she is mostly distraught because she had thought herself a changed and improved person since returning from Mei-tan-fu. Her interlude with Charlie has made her feel no better than she was when she left.