I think your issue is more with the conservative interpretation some authors have of independent women. I’m not surprised you read novels about strong female characters becoming helpless females once settled down. After all the idea that women are supposed to stop working and take care of their husband / housework / kids isn’t still very present in Asian cultures. And even tho houses wives can be awesome (because the work can be endless) some also portray them as idle or helpless. I think authors who make strong females characters weaker after settling down have this biased view that a female should rely on a their husband and are then dependent of them. So if you see your favorite character loose all traits of independence it’s not because of a relationship itself but because the author’s interpretation. Hence saying that MC would be less independent once with ML is a very distorted view. A real strong female lead will stay strong independently of who she is with and her partner even if charismatic will only compliment her character and not overshadow it. If it’s done right. Lol
I feel as though you have taken the author’s intention the wrong way. I think that the author had portrayed her to sleep around not because she is a woman and sleeping around is bad, but because it shows that she is indulging in her pleasure instead of taking care of her people and letting the people close to her be executed, while trusting the duke who is kissing her ass.

who is the ML?