Okay...
So long as you think I'm okay so far, let's throw in some external factors that, while there isn't really much I can do about them, may impact everything to an extent.

I have a friend (I'll call her Melanie) a year younger than me (two years younger than Ben) who I recently started talking to again. Our circles of friends don't really overlap anywhere, so I wanted to integrate her with Ben and me. She's been mistreated from some of her friends who have their own problems, so she's in need of some well-adjusted friends.
I invited both of them for a sleepover at our cabin of sorts out of state. From Saturday til Sunday. Melanie and I used to always have sleepovers, and then we drifted, but I thought having another sleepover would be a good way to "re-break" the ice.
Co-ed sleepovers are something relatively new to me. My parents were originally in on the idea of a big sleepover with four of my friends, two other boys and two other girls. They figure it's okay so long as they know they can trust everyone there.
Recently Ben's started sleeping over at my house. He used to walk a block or two home at one in the morning, so my mother was the one who suggested he just stay the night. We sleep on my corner couch, so it's no big deal.

Anyway, my parents "observed" how we acted around each other, meaning they basically passed judgement on us... And they concluded that Melanie likes Ben. I don't think this is the case, Melanie has denied it, but it opened up an entire argument with my mother.
Suddenly she was exploding with opinions and advice about my social life. How Melanie likes Ben, how he likes me and is just waiting for me to say something, how I should show him some gratitude or something to that effect...
Now, as far as I know, Melanie does not like Ben. But I think that if he gives her the acceptance she craves, she may confuse that gratitude for attraction. Since he will probably be the first guy to take her seriously, she may develop that liking for him. But we'll see.
He doesn't like me. Everyone seems to think "it's so obvious," but it's been brought up time and time again, and he's stated that he doesn't like me like that.
And I most certainly don't owe him anything.

Question is, how do I stop my mother from judging? I'm sick of it, and my friends are, too.

Plus, I'm beginning to feel that my relationship with Ben isn't really mutual. There's definitely a bit of a block. Ben's best friend is a senior this year, who I'm going to call Cassie. They dated two years ago, but now they're just friends. Cassie has a "new" boyfriend who's a little older than she is. Apparently that's what she looks for in a relationship.
Now I'm kind of making assumptions here, but it seems like Ben still clings to her. I have no idea how their romantic relationship ended, and it'd be interesting to know, but it seems like Ben has more of a need for Cassie than she does for him. Although I like Cassie a lot, and we get along just fine, she seems to put a damper on my relationship with Ben.

Also, Ben wants a psych major when he goes to college. Even though I too have an analytical mind, sometimes when we're having a conversation I can't help but feel like he's testing me... How do I deal with that sort of thought?

Anyway, thanks so much for taking the time to read this. It's confusing, I know, but I really appreciate the help.