I've to commend the Empress she went through a lot. Despite being there for her sister initially, her good intentions won her favor with what is now the former Emperor. It's clear as day how weak-minded he was, and honestly, he should never have been Emperor. Considering how forward her sister was I can assume he became a Lolicon because younger girls were less assertive, but still showing kindness.
As the years went on, the Empress became like the other older woman that frightened the former Emperor. Her rape of the former Emperor really gave her a reminder of him and not to forget her. Granted, she might have scarred him for life. Though this is one case where your ask do the ends justify the means.
- Obviously the emperor was pissed off and in pain when the former Emperor forgot her. It is hard to say if she loved him, but I assume when she birthed a baby and to go unnoticed was more so the thing.
- Still you could assume that because of those actions the former Emperor put himself in hiding. As a result, many girls that would have been exploited were not. Even if that was not the #1 priority for why she raped him, given her personality and how in the flashback she seemed to be disgusted with him, that could also been a motivation.
Still, at the end of the day, it appears that the Empress was in that painting. Despite a fukked up story, I guess there is a positive note in this. As the Empress sees the former Emperor in Jinshi. Now, as others have pointed out, we see clear reasons for the baby swap. Regardless if Jinshi is the current Emperor's younger brother or son, the love of the Empress has for him is true. More than likely, Jinshi represents the former Emperor if he grew up in the right environment.
Would the Empress show the same love to Jinshi if she baby she had from the rape we see in this episode? Just the comment I have been watching you for a long time just gives me the feeling Jinshi is her grandson. Also, she knows his dynamic with Maomao given the end of the episode.