Why do females do this to other females like seriously?

Ok. I went to the drug store with my mother cause she wanted me to come along what have you. I said ok ill go. knew it was a bad idea. Today i wore a cute grey knit top with earrings to match jeans and some cute sandals. You always have to look your best because you never know when you gonna run into somebody you DONT care to see. So we went in and as soon as i got in there this lady turned around and looked at me and looked me up and down and i just looked at her like is there a problem and just kept it moving to the makeup aisle while my mother went and got whatever. The lady had on an oversize shirt and some shorts didnt check out her shoes .The make up aisle is like 2 aisles away from the cash register. Then i heard somebody talking and she was describing my outfit to the tea and talking about i dont know u had to come dressed up to a drug store and was going on and im like wow are you serious. Im like i dont even know but if i had came with a tee and some jeans and looking kind of rugged she would have said something. so its a lose/lose. I'm over it now but it kinda got me a little upset. Btw maybe this might be an issue i live in a small country town , they are kind of behind on fashion.Why did she feel a need to complain and talk about my outfit?