"She be coming"
Is this archaism, colloquialism,

Hmmmmm, a holdover from the earlier English that came to us in the 1700s and is still used in more remote pockets of habitation ?
Phrases similar to "she be" are sometimes heard in old Bluegrass Music that are based on early English songs.

Musick : can you help us out here?

Would this be a colloquialism ? I don't think that'd be the exact appelation?

And how'd you contract "she be?" She'b ????

Oh,dear! another disappointment from Enigma ..thought it'd want esoteric Sheba for "she'b" but instead got plain old "she'd." [sigh]