I'm completely losing interest in her and planning to stop talking to her
Why have you been feeling disinterested and wanting to stop talking?
I'm just bored of her, she doesnt have any intellectual conversations
If you feel that a relationship is not working out then it is fine to stop talking to someone. Just let them know how you feel beforehand.
I will let her know, I think this is best for the both of us.
Staying in a relationship where you feel it is not working out is bad for the both of you. It is good to recognize where you may not be working out with someone.