"Can she take a deduction, and would it be on Sch C or Sch A"

When a business has waste (damaged goods, out of fashion and no longer sellable, dangerous material that should not be on the market, whatever), that is part of COGS for a business. Businesses don't have "donation" as such.

Sched A moves that to personal. That's why you have the warning about double-dipping. It can't be both.

"She has amassed a large amount of unused raw material (over $25,000)"

Cost or value if they had been sold? Because you cannot write off what was never written on. You cannot claim $25,000 value in either Schedule. You would claim it at cost. Or, the business would claim a sale and a 100% discount to the charity, which then has proof of value for their support needs, but the business still has:

Sales income minus cost = profit, which got written off (such as the Returns and Allowances provision on Schedule C)