Well that sounds like a great start.
Sounds like all you have to do is slip the halter on. If this is the case then once you get the halter on then I would leave it on her for a few days (providing theres nothing around for her to get hung up on). I know a few people that even leave a lead on, this way she is easy to catch (although that doesn't sound like that's going to be a problem...lol) and it teaches them to give to the pressure - she steps on the lead (not so long she can get tangled in it) and she lowers her head to get away from the pressure.
I'm not sure if this is the kind of ideas you were looking for or if you wanted different things to try with her when she has the halter on?
I put a halter on my baby when he was a week old. You just have to make sure he can't get caught on anything. And always check that the halter is fitting still. I never left the lead rope on him.. but I have other horses. Like a 2 yr old filly I got that wasnt halter broke at all. Letting her fight her own pressure was easier than mine. And I taught them to walk by applying pressure to the lead and also looping the lead around the butt so I could kinda pull if need be. Once I got a step I loosened and Praised. Then next time I asked for 3 steps. And so on.