Why would she engage in casual sex if she doesn't want or enjoy it though? Why would she encourage Tav to do it either if she doesn't consider it to be a good experience, but merely something she was "trained" for?
She also implies in this convo that she never wanted a swan. Yet in another conversation, while breaking up with you over Karlach, if Tav says they aren't a swan and they want to be with them both, Shadowheart rejects you. So which is it? Does she want a swan or not? Because two different conversations contradict one another. SH has even shown attraction to Karlach, so why not join a poly relationship then?
And where does SH date more than one person at a time? Who else does she date?
Ehhh also makes a solid point: "I would always want more of you than you'd have to spare" is a done deal. This right here is the icing on the cake.