Joy,
Catecholamines (adrenalin, etc) are documented to interfere with smooth muscle
contraction.  I would imagine that unrelieved pain could prevent milk ejection
on this basis alone.  Mom is probably doubly traumatized because this birth
experience is farther from what she planned and envisioned than if she had
expected a medicalized US-style hospital birth.
        I once saw a mother for inadequate milk.  I always ask about the
birth.  This mom launched into a long story of many unneccessary interventions
done against her will.  I reflected back to her that it sounded like she felt
like she had been raped.  She immediately started to cry and agreed that that
was exactly how she felt.  After a good cry, she pumped well and nursed her
baby, and did fine thereafter.  Just a thought that something similar might be
bothering your mom.
        To put formula in perspective, I often tell moms who must complement
that starvation is far more harmful than abm.
Catherine Watson GEnna, IBCLC