I read that as an insult. Better no card than an insult.
I know the relationship is strained between you. But this is not just your day or hers, it is both of yours. I recommend that before the big (or nothing) day, you ask if she wants to celebrate the good times that you had together over the 15 years, maybe by meeting for a drink or going to dinner. If she says no, fine, then you have your answer. Do nothing. If she says yes, then go to dinner, and only talk about the good times. Make it relatively short, and go to your separate homes afterwards.
