Absolute power corrupts absolutely. I think Atris became so blind with power when she was on the Council that she assumed it meant she was perfect and always right. Part of her anger for the Exile was that she wanted to feel superior to her and when she showed time and again that she was the stronger one.
Wouldn't it make sense that Atris hated the Exile because she was always going to be stronger, despite all that Atris had going for her. Why do you think Atris was too afraid to fight the Exile the first time on Telos? No matter what you did to provoke Atris, she kept giving empty threats of which she never delivered. In truth, Atris was just a power-hungary tyrant who knew she would never become the greatest jedi, so she moved to have everyone else killed so she was the only one left standing. That's why she betrayed the jedi on Katarr, but never went herself.
I hate arrogant, self absorbed, power mongers and that's exactly what Atris was.