Should I fall into this or just ignore her?? NO RUDE ANSWERS!?

Everytime I go to my local grocery store this girl who used to go to my high school works there she ALWAYS look at me with a really hateful look usually I would just look at her and laugh in her face because she's really not that attractive and Im just assuming it's jealousy tbh because the thing I don't understand is how could you hate someone who haven't even said anything to you?? Anyways I plan on going there again today to grocery shop with my mom and if she does this crap today I plan on asking her what's her problem and maybe even slap the **** out of her *** !! I don't want to make a scene at the store but this what it seems I have to do to let her know I'm not the one to be playing with!!!!! What would you do???