I agree with Mollie, Fenugreek and Blessed Thistle are good. Blessed Thistle can be hard to find though, Herbs of Gold make a Breastfeeding Support blend that combines both herbs. Brewers yeast (lots of that in the lactation cookies) is good too, so she can even put that in drinks etc. A friend was recommended alcohol free beer as well. Actually I wonder if those new Bundaberg brewed fruit drinks would help... although the citrus could cause taste issues/curdling.

Spending time skin on skin... if she can, take a break from life for a day or two and just feed feed feed whenever he wants it.

Would she feel comfortable leaving out the formula for a day and seeing how he goes? I was surprised when I was able to stop comp feeding when DD was about 2 weeks old. I didn't think my milk would ever be sufficient.

I did end up having more supply issues later and started expressing between feeds to boost supply. In hindsight I should have just popped DD on the boob rather than pumping because the stress and fatigue of the whole merry go round really tanked my supply.

Good luck to your friend, and good on you for advocating for her.
xox