Everything upstairs is wrong. The supplementary card can only be applied for and handled by the cardholder of the main card, so you should note that the bank only recognizes that the application form was filled out by your mother, and the relationship column must be filled in (ticked). The application form can only take effect after your mother signs it and you sign it. In other words, if your secondary card is successfully processed, your secondary card and main card will use a credit line. Moreover, the main card can control the usage quota of the secondary card through the bank. As long as the main card agrees to apply for the secondary card, as long as it meets the requirements of the bank, it will definitely be approved, because the creditor's rights relationship of the secondary card is uniformly borne by the main card holder.