I had a breast reduction about a year ago, and my guess is that the pain is due to her changing nipple size tweaking scar tissue and newly connected nerves.
My nips were so sensitive for a few months after the surgery that I couldn't even ride in a car without pain...the vibration of the car would cause my bra to rub minutely against my nipples and boy, would it hurt!
Please tell your daughter that some women are able to breastfeed sussessfully after BR. Much of it depends upon how much glandular tissue was removed, and whether or not she had a free nipple graft (which severs the ducts), or if her nipples stayed attached during the surgery. She'll want to work closely with a lactation consultant to make sure the baby is getting enough milk. She may need to supplement with formula, but some breast milk is better than no breast milk.