Actually, if they think the incest patch make her dominant on Marc and complain about it, means they are taking the wrong choices in the incest patch.I read some posts from some users citing precisely this fact that Myrian has a very dominant stance over Marc and with the incest patch they say it gets even worse, but as you mentioned this is just a game, sometimes I don't understand these claims.
Wrong for them I mean, there are people that like the idea of Myriam doing stuff with Marc and being dominant.
I use the incest patch myself (but also explore other paths, to check and because I like other "kinks"), but I follow the path in which Marc is dominant, or at least "pushy", and Myriam goes in her sub/mislead protective mode to keep him happy, to help his morale, and at a certain point has to start admitting she gets excited at some behaviour and words.
Even in that path, I disagree with the idea that Marc is the same as Anthony, but anyway, in that case defintiively it cannot be said that Myriam is dominating Marc.