It's not that simple, she lactates for 2 reasons:
- Pregnant; and/or
- Have "(MOD) Breast A" applied.
The Seedbed state itself doesn't cause her to lactate, it's more of a permanent state of being pregnant.
EDIT: The easiest way would be a script that constantly sets the lactation amount to 0, since if either of the 2 reasons above are true, lactation increases by a variable amount.
If there's enough interest in such a function, I'll add it as a new addon module for Modular Cheats Mod. (Though it might increase lag if not done right)