Should I have friends who are "smarter or at the same level of intellect"?

I just got in an argument with my mom about the people I hang out with. I find it so ridiculous that she's telling me to hang out with people who are smarter than me so I can "improve myself." I don't drink, I don't do drugs..and I'm 18. They are my FRIENDS, I like them, they like me, they're GOOD people. Is this so hard to grasp? Besides, I believe everyone is smart. She doesn't even know them. Just pisses me off..What are your thoughts on this? I appreciate the feedback.. :) x