Start buying lots of protein and eat more when around her. When you do it behind her back and start bulking just tell her it's the protein.
Inject in your leg and ass and if she says no, your juicing, tell her "The only successful way to inject is in the shoulders because the shoulders are the only muscle that does not have random nerves and blood vessels that could be poked, and look at my shoulders, no marks!"
Just lie a little - if she's worth it that is.
I told my girl I was juicing and she didn't care for it, but when I told her how much I had learned, she was better with it. I told her when I have 15 more lean punds on me and other ladies are hard staring when you are with me, you won't mind so much. She agreed.