Goth Girlfriend

You have only been with her for only a week, and you absolutely love her. She is very loving and caring. She lives with you now, and she helps with you and stuff around the house. But you wonder if you should tell her about your preference. She is already beautiful. She has a big chest and a bit of thick thighs. She wears some goth accessories and has dark brown hair. But you want to see what she will look like, as bbw. Can you make her fat on purpose without her knowing? Or tell her what you want?