How do I convince my younger sister to take kickboxing cles.......?

So I have a younger sister, 14 years old and I do get pretty protective over her sometimes even though I try my best not to show it. The thing is, I know I won't be able to be there for her everytime and since I've started taking MMA cles I want my sis to take some kickboxing/conditioning cles as well so that if there's someone trying to mess with her she can kick his @ss and walk away without getting hurt. I don't know how to approach her over this issue though. I mean she loves working out and kickboxing will keep her in shape but teenagers are really rebellious nowadays. What can I say to her to make her understand that this can be used for her own safety?. Thanks.