Is it okay to purposely sabotage my exes new relationship
I don't think you should. Is there a reason you want to sabotage the relationship?
I'm going to do whatever possible to make her suffer
There is no valid reason for you to actively try and sabotage someone elses relationship. If you think that you don't like that person then you should do your best to remove yourself from that situation.
I just want to feel good about myself knowing that I've made her feel like shit.
I know breakups can be hard and make you feel bad. I think you might feel better if you just move on from the relationship and distance yourself from any contact or reminder of her. Sabotaging her relationship will do nothing to help you heal.