You could be telling the truth. So she should dump you. You could just be wanting excess drama in your life. So she should dump you. In any case, you're 99% positively a manipulative dick. So she should dump you.
This is just as bad as doing a fake proposal prank. If a guy ever prank about cheating or proposing, I would seriously break up right away.
If there is something you don't joke about is real life altering events. How would you like it if a girlfriend pranked you about getting pregnant or by using a fake ultrasound and then told you ''it's just a prank''?
Only if you want to end the relationship. Some things are too important to ever treat as a joke. How would you feel if someone pranked you by telling you that you mother had been killed in a car accident?
No that's a pretty bad prank and no one would appreciate it. Pranking your girlfriend is when you do something that scares her and gets her heart pumping. They yell at you for three seconds afterwards and then start laughing because the adrenaline feels good.
This is idiotic. It's not funny, it's extremely hurtful, distressing and disrespectful. You'd be extremely lucky if she didn't dump you even after you revealed you were 'joking', and you'd have done permanent damage to her perception of you.