How to tell gf about ur kinks ?

So I’m 23M and I’m really into ball-busting I’ve been dating this girl 24F for 4 months now and she’s really kind and attractive I’m a quiet guy always have been we’ve discussed a few kinks already and made a lot of jokes about a few but I’m scared to tell her about mine if she finds out the quiet kind guy she’s dating wants his balls crushed and flattened she might get scared and leave.