it is best to let her come back on her own if you find her close by, sence she is probably use to being in a pen that will be to your advantage, now if you see her on the ground try to get behind her but stay back a little just close enough to have her going forward, walk towards her slowly , if she goes to the left and you don't want her go to the left and walk closer to her causing her to go back to where you want her, it is called herding do the same thing all the way to the pen till you get her to go in and she will probably go in willingly, bring a long stick or pole in case she gets under something and make sure the gate is open to the pen.
If she gets to far away you can set up a pen and put feed in it and herd her that direction, i use chain link kennel panels with the gate left open or even a panel unhinged on one side .
Make sure you cover the pen so she don't hop out.
If something spooks her in a tree she may not come down till tomorrow sense she is now lost and scared.