(Repost) Why does my coworker always get butt hurt when someone doesn't like her?

I saw this little girl that's in my classroom at the preschool I work with. She screamed with excitement when they say me and hugged me. My coworker and friend said hi but she didn't answer and ignored her. I was like, "Say hi to Miss (let's call her Laurie)." They didn't and talked to her. Okay...oh well not everyone is going to like you. She looked hurt, but I put my hand around her shoulders and told her, "It's alright Laurie. Not everyone is going to like you. But there's some other kids that like you. So what if she doesn't like you?"
Not a lot of kids like her. She is mostly serious and the "disciplinary" so I don't know if it's that or her size (6ft, broad). She shouldn't worry what people think.

Even I get more excited to see my best friends over my other friends sometimes. I don't think it's rude.