Why does my coworker seem to ignore me and engage to other coworkers. What is wrong with the picture?

One of my coworkers (well ex coworker now because I resigned today for personal reasons) could not stand me at all. She seemed to be uncomfortable around a special needs adult. She never looks at me when I speak or when I say good morning, she gives me a dull good morning or ignores me. One time the other two coworkers said by and have a good weekend and she just walked right passed me and ignored me. I didn’t do anything to her. She never shared her interests with me but only to them and the others. When I thanked her twice, she doesn’t respond at all, but with others she responds with “you’re welcome” or “no problem”. She does with the kids too. I felt like every time I come in, she has this “Oh great she’s here.” Or “I dislike her/him.”
She got frustrated when I didn’t get social cures as quick as others or when I tried to help, she scolds at me for not getting the social cure. She did help me with how to have more patients with the kids though but she can’t stand me.