Downgraded from paid First Class

I purchased a first class ticket for my mother to fly here for Christmas. Less that 24 hours prior to her flight she gets notified that on her first leg she’s being bumped to main cabin on an RJ. Thankfully it’s only an hour flight but she’s 76 and recently had back surgery. The whole reason I got her 1C is so she would be comfortable. Delta is offering to refund the fair difference and give us a $200 voucher, but that seems sort of cheap. Any advice on making this a better situation?