After having succesfully shrunken one of my combatants (Miredesi), the Wildling shaman continued casting Shrink on Miredesi.

Maybe it figured Ceresa's spell resistance didn't make casting against her worth it, but it was less worth while to cast shrink on Miredesi, instead of engaging on melee.

Playing on Challenging.

Below is excerpt of battle from debug.err:

Debug Message: TacticalMapViewWindow::FinishInitMapGfx finished.
Debug Message: Tactical Spell cast: Shrink_Ability at 12, 18 by Darkling Shaman (unitID 390).
DebugMessage: Loaded font Segoe UI-27BoldItalic
DebugMessage: Loaded font Tahoma-9Bold
Debug Message: Tactical Spell cast: BowAttack_Flaming at 16, 13 by Miredesi (unitID 326).
Debug Message: Tactical Spell cast: Shrink_Ability at 12, 18 by Darkling Shaman (unitID 390).
Debug Message: Tactical Spell cast: Shrink_Ability at 12, 18 by Darkling Shaman (unitID 390).
Debug Message: Tactical Spell cast: BowAttack_Flaming at 16, 13 by Miredesi (unitID 326).
Debug Message: Tactical Spell cast: Shrink_Ability at 12, 18 by Darkling Shaman (unitID 390).
Debug Message: Tactical Spell cast: BowAttack_Flaming at 16, 13 by Miredesi (unitID 326).