Since her right heel is up, I'd say she's walking and, unless french girls are more often mouth-breathers than not, I wouldn't call that expression "lost in thought".
I'm not sure you can conclude the whether the sun is rising or setting either.
If I took a whirl at mind reading, I'd say the expression indicates:
If morning: "Crap, not only did I forget my shoes, I came all the way out here with my sickle and there's nothing to cut!" (note the bare field)
If evening: "Crap, I left my bundle behind!"
Well after caddying for the Dalai Lama (Big hitter the Dalai) he felt he was going to be stiffed on a tip he asked
“Hey, Lama, hey, how about a little something, you know, for the effort, you know.” And he says, “Oh, uh, there won’t be any money, but when you die, on your deathbed, you will receive total consciousness.” So I got that goin’ for me, which is nice.
Whatever time of the day it is, I’m thinking “Did I forget to turn off the oven”
“Is that a weather balloon, or is it a UFO?
Seriously, it’s a beautiful painting, and I can see how Bill could have gotten inspiration from it. Good for him.
By the way, that song Jerry Lewis used to sing at the end of the Telethon had the lyrics “the song of the Meadowlark”……