I'm pursuing this girl that my friend is interested in.
Why are you starting a relationship with this girl?
I'm tired of hating and fighting with my girlfriend all the time. I need a new girl.
It's wrong to get involved with a girl that your friend is also interested. It's even more wrong to do so while in a relationship already. Your friend and girlfriend would both feel betrayed by you if you pursue this girl.
I think it'll be okay since they can't even stop me. Also they are both stupid.
You are so wrong here. You are betraying both your friend and girlfriend.