Is it okay with how I want to tell my best friend her other 'best friend' hates her?
Of course not, it sounds like a bad joke to me. What is the reason you do such a thing?
One of her friends dared me into doing this.
It is rude to lie to make people upset. You should hold fast and keep your nose out of problems.
It's just the best way to get someone out of a group since that other person already hates her.
This is sounding a little too high school for my tastes. This scenario is just something that needs to have more tactfulness so people don't get their feelings hurt.