Don't give it a second thought.

You've probably spent more time thinking about her than she did thinking about you.

She was a cute blonde girl in a mall. She very likely;

A: Saw a guy whose attentions were much more welcome than yours.

and

B: Saw a guy whose attentions were a lot more unwelcome than yours.

and

C. Spent time chilling with friends whose anecdotes are probably occupying her thoughts right now.

In short, she's a busy girl who can't remember everyone she saw today.

As for the possibility that this was a junior version of Jean Grey who was able to "detect" your sidelong glance with her mind; an unconscious head turn might've given you away.

When I was in HS, I was obsessed with not seeming obsessive. I thought I was so stealthy in sneaking glances unobtrusively. And perhaps I was. But my brother once critiqued me from the backseat of a car we were both riding in.

"Your head turned."

"Did not."

"Did so."

Anywho, why speculate about her motives or feelings? Some girls just want to confirm that they're desirable. They can't quite believe it.

Others might feel the attention was unwelcome. But since you seem overlikely to come to this conclusion on minimal evidence, I'd dismiss it if you didn't hear or see anything overtly negative.

I the absence of further info I just leave such speculation aside and enjoy.

Now what's really fun is when you're looking ahead minding your own business and the girl passes you and then looks back over her shoulder. Its rare as all get out for me to be on the receiving end of such a glance accompanied by a smile, but my AG crush Sarah did it once.

Dante