Starbucks scam

I work at a Starbucks inside a Ralph’s and I’m fairly new but there are regulars who have been coming in for quite some time and they get charged a specific amount and there’s this one regular who brings in her own Trenta cup and wants nonfat milk to the top line w an added shot and 6 pumps of mocha. She would get charged $3.25 for this.. mind you we don’t do trenta frappes. Shouldn’t i be charging her for a mocha frappe which would come out to $6-$7 w the personal cup discount? I’m the Starbucks leader and i just don’t think it’s fair what she’s doing.