lol, I did the exact same thing. I was ecstatic how fast mine learned, but still to this day whenever I pick up her front feet she tries to bow. Really makes the farrier mad, hehe.
What I do it first teach them that a tap on their leg (where ever gets best response) means lift her leg. Do it until its very clear and that she might hold her foot in the air. If she goes to put it down, tap it up before she sets it down. Your timing has to be quick. From there, you need to teach her the "stance". She needs to learn to stand spread out, with her front legs much more forward than usual. She needs to develop balance and symmetry in that stance before you can effectively teach bow. Teach her that when you tap a different part of her leg that it comes forward.
Once she has learned to lift her leg and hold it, while in "stance" you can start to incorporate her rocking back in preparation to bow. Stand facing her, tap her leg up, and rock her weight back. Reward for her shifting her weight, don't get after her for putting her foot down. She will soon workout how to rock back slightly with her foot in the air through repetition. Once she can hold her foot up, and rock back without slamming her foot back down you can start to rock her back and correct the leg when it wants to drop.
Be careful not to over-do it, reward big for little efforts and each day you will notice her catching on. Small accurate sessions will get you there sooner than long strenuous ones. :)
In riding, a horse's energy is like a river- guided by the banks but not stopped by them.