I just need to find the right one. I need one that says:
"Congratulations on the whole wedding thing" while at the same time also saying "good gods girl why would you do this? Were you drunk?!" and "STOP! STOP! IT'S NOT TOO LATE!" with a nice subtext of "when the time comes, I will help you bury the body."
And, of course, "just because I'm willing to help you bury the body doesn't mean that, in 18 months when you realise what an arsehole he is, I will be saying 'I told you so'"
See this is the problem with cards, they lack eloquence.
Maybe I could go with a cake - it could be full of butter and sugar symbolising something you will definitely regret later with a heavy lemon kick for the bitter bitter regrets that are sure to come and maybe some spiced caramel for the warming assurance of murderous support in the future.