Ivanova was a pain in the ass in season 1. always telling a new young telepath to stay away from the Psi Corps. She should have just minded her own damn business and let the new young telepaths find out for themselves if joining the Psi Corps is a good thing or a bad thing to help the out with their new telepath abilities. She kept blaming the Psi Corps for her mother being a druggie
Ivanova's mother was NOT a druggie. She was forced to use telepath blocking drugs, by law. Her only other options were joining the Psi Corp or prison, but she didn't want to be away from her family, so she opted for the telepath blockers.
They had the unforrunate side effects that Ivanova described, especially after taking them for years and years. Everyone has a breaking point, and Ivanova's mother reached hers and took the only option she felt she had left... suicide.
Given the things we saw the Psi Corp do with regular people
and their own telepaths, and what Susan went through, I completely understand why she has such an intense hatred of the Psi Corp.
They were the bad guys, through and through. I think the only decent members of the Corp we ever met were Jason Ironheart and Harriman Gray. (Outside of Lyta and Talia, and Talia ended up essentially dead once the 'sleeper personality' took over.) Every other member of Psi Corp was a bad guy... especially Bester.
Side note: one thing that made Bester such a great character was that if you look at it from the angle of someone going to extreme lengths to protect his 'race', he's not a villain. In a way, he's almost a softer version of Khan Noonien Singh... he looks at non-telepaths as inferior, just as Khan looked at non-augments as inferior. The difference being Bester was more about protecting telepaths and staying seperate from mundanes... with Khan, it was make eveyone his slave or they die.