Halter training

My new filly, Ariel, wasn't handled until my father-in-law bought her momma. (She is approximately 6 mos. Old). I'm reading lots of different things to halter train/break/whatever, and I'm wondering how you all would approach this situation? I've never halter trained a horse before, so this is totally new.

Here is what I've done up to this point: I spent a lot of time just getting her used to me, by scratching, rubbing, hand-feeding, etc. When she showed up, she wouldn't even let us get near her - she would hide behind momma (oh, she's not weaned yet. When she's halter & trailer trained, she's going to live on a pasture to play with momma and two other mares, so there is not much of a point in separating them at this point. I would rather work with her everyday and get consistent ground manners, etc, but my current housing situation doesn't doesn't allow this set up. I hope to bring her back as soon as we buy acreage... but I digress...).

SO - I can put the halter on and off now and she doesn't care. I've started pulling on the lead and walking away, and she comes (mostly because I have grain in my pocket and she knows it). What is next? I really look forward to your advice!

Sorry - by pulling and walking away, I mean only a few steps and very gentle pulling from side to side. And only in her pen. So I take say three steps sideways and pull a tiny bit on the rope and she comes towards me. Just wanted to clarify... not sure if I was clear enough to begin with...