They still keep the record of all the information you provided, likely including email, name, what you purchased, with what payment method, and more. They will be able to make statistical inferences of your socioeconomic status variables and can and will resell that data to others who will absolutely not give a shit about your unsubscribe status. In the end it may be worth the 15% off for her, but it is definitely not scamming them by unsubscribing.