What is the ruling on using a discount card that the questioner obtained from the company (Yves Rocher), which specializes in selling creams, given her knowledge that non-free subscription in such companies is forbidden, and that she obtained the card indirectly when purchasing the company’s products, and not with the intention of subscribing?

If the reality is as you described, then there is nothing wrong with what your friend did, because she obtained the card for free without paying any consideration or making a purchase to acquire it. Rather, she had an intention for what she bought, and the money was paid for its purchase, and the store donated the card to her. Therefore, there is no influential deception (gharar) in her transaction with it.