This episode is on p. 137 of Cogitosus' Vita in Acta Sanctorum
(February vol. 1).
A wild boar besets what the text calls a grex ("flock")
of pigs. Here of course we have a flock of sheep. Pigs or sheep,
the saint's response is the same. She blesses the boar, and then
in the upper register we see the effect of her blessing: The boar,
no longer wild, grazes peacefully among the other animals.
The herdsman in the picture is absent from Cogitosus.