You should only be responsible for the amount of when the divorce was finalized. If the card had $5000 on it then and now it has $15k, that other $8k is not yours. That is hers after the fact and now separate.
Who "owns" the cards?
If you need help, please advise. SW Legal Services 623-251-7201 www.swlegalservices.com dawn@swlegalservices.com