I would simply section her mane off in four or so (depending on how thick her mane is) sections and do very loose regular braids. Or a running braid, although I have found that no matter what, my running braids NEVER stay put when the horse is turned out. At all.
I leave my horse's mane in a running braid pretty much all the time and haven't had any problems with it falling out, getting snagged, or anything like that. But, my horse's mane is REALLY long (like 2-1/2 feet) I cut it back to about 18" last winter and did notice it would start getting loose faster at that length.