How to reply to this very rare argument?

I think I've heard of this argument once a few years ago and I didn't really know how to reply it.

The non vegan's argument was "If a woman is vegan and gives birth to a baby, but can't lactate, what does she feed the baby with the first months of their life if she can't use milk formula made from cow's milk?"

I know that cow's milk is extremely unhealthy and that mother's milk is essential for both the mother's and the baby's health, but in case she can't lactate, I don't know what is the solution I can propose.

I've heard there are situations where some mothers might share milk with other mothers if they can't lactate, but I don't know if that's always an option, and if not, what would be the best solution/argument to not exploit cows for such cases?