Do you think I should not include my friend when I smoke with my boyfriend?
Why do you want to exclude your friend?
Because my friend doesn't make good choices. I want to have a good time with my boyfriend and my friend won't exactly enhance the experience, to say the least.
You can choose to do whatever activities you want with whomever you want. I think it's common for people to want to spend more time with a boyfriend than a platonic friend.
So it's OK to leave her out? It's not like we'd be shunning her from our lives entirely.
Yes, you have a right to arrange your private times with your boyfriend. If your friend asks, just explain that you both care for her, but sometimes you need time alone.