I would like to seek your guidance regarding the permissibility of using a store fidelity card under the following circumstances: There is a shop that

Question

I would like to seek your guidance regarding the permissibility of using a store fidelity card under the following circumstances: There is a shop that sells a fidelity card in the customer‟s name. By purchasing this card, the holder is entitled to receive discounts of approximately 50% on items in the shop. If I purchase this fidelity card in my own name, would it be permissible according to Shariah for my sister to use the same card so that she may also benefit from the discounts, even though the card is registered to me?