She definitely did **** wrong. Within the past 3 years, she's insinuated that HHH was abusive and raped her while together. That's just one instance. If you Google you'll find more.
WWE fired Chyna because of the situation, not because anything substantial actually happened when she found out HHH was with Steph. There's almost no way she's dead right now without that humiliation.
Yeah I'm with iso in feeling that both sides did some ****ty stuff. AFAIK Chyna wasn't an issue during her time in the WWE, she was basically released because of Stephanie and it started a major downward spiral that led to her becoming a pretty terrible person. I don't put the blame solely on HHH/Steph though because no one is responsible for the decisions Chyna made other than Chyna.
Compare her demeanor in these two interviews. There was always something not right about her but she's a mess in that X-Pac confrontation.
Chyna is the worst. You can talk about people possibly trying to ruin her life by blacklisting her from WWE but there is more to life than WWE. She was actively making up stories accusing people of domestic abuse and rape. Thats just wrong and effects more than just your ability to work for one company.