I think ruling an entire people goes against everything she stands for anyway. If you remember the flashbacks from the episode "Old Wounds", Suyin believed in freedom and individuality. She hasn't changed that much and her philosophies are literally the opposite of Kuvira's. That relationship was doomed from the get-go.
I wasn't really surprised she changed on him. She done put him with mad shyt. Working her like a slave for 3 seasons now. "Zhu-Li, do the thing"
shyt was executed and written so well