"She talked only about herself the entire evening."
Translation:Celý večer mluvila jen o sobě.
"Celý večer jen o sobě mluvila." with normal pronunciation means "She only talked about herself the entire evening.". The meaning is different. Also, even that is more naturally said as "Celý večer jen mluvila o sobě.".
If you stress the last word "Celý večer jen o sobě MLUVILA." it will mean the right thing, but stressing the verb this way is very unnatural. If she SPOKE about herself instead of doing what else about herseof?