I made my sister's friend leave town
Is it because you hate your sister's friend or your sister?
I hate my sister's friend. I believe this way is better, I'm tired of seeing her.
You have hatred towards someone and it shows. To make them move because of it is really not right of you, if she is too far away from your sister then their friendship might dissipate. Ignoring her would have been a better idea.
It'll be fine. I did the right thing.
Whether you like your sister's friend or not, you are better off not interfering with her. You are not the one who is hanging out with her, your sister is. You trying to make her leave town is only going to make your sister upset most likely.