Fortunately the weather cooperated and I got to work with Gwen last night. I almost had to chuck out my plans though, when she didn't want me to put her bridle on. Immediately I was worried about her being in heat, riding a Gwen in heat is a no-no in my book. Fortunately I figured out she was just hungry, when I showed her that she was still going to be able to eat hay she was fine with it.
I spent a few moments just sitting on her, letting her eat, until she started looking around at me. "Okay, you're up there, now give me some treats." I very gently tapped her with my calves and said "walk" (see, I do take your advice). She thought about it for a second, then slowly stepped forward. After rewarding her for that, I asked 2-3 more times until I got a much bolder step forward. Click, treat, and dismount. Good girl!
I'll let her cogitate on that for a day or two before I climb up again. When she steps forward boldly as soon as I touch her I'll start asking for another step. Eventually I have plans to set up some cones so she can get the concept of traveling from point A to point B, but I'm taking it super easy for now.
I don't know what I'd do without clicker training, I wouldn't have the guts to climb up on her without it.