That was just a dream, specifically her dream. We'll probably see rougher content with her as things progress further and she understands herself better, though it will be because she wants that,
I am not sure that she does. If anything I would say the opposite. What that dream shows us is not what her sexual desires are but how she feels about her self.
Remember that conversation she had with her relative just before the big blowup that lead to her being brought to the house. She was told in no uncertain terms that she needs to start earning money to pull her weight around the house. And her response was to blow up like a teenager. But deep down she knows its true. She wasn't useful. She was not pulling her weight.
That dream represents her image of her self. She sees her self as useless, unable to contribute. As someone who is just a useless burden leaching on the hospitality of others. She probably felt that way for a long time before being confronted. And thus the logical conclusion for that in her nightmares is that they would turn her into a useless whore to be sold for cheap money. After all, she isn't good for anything but even useless can fuck.
That is why she is so desperate find some use around the house. So much so that the house magically starts producing dirty dishes and dust for her to clean. And it's why her approach to sex with the MC is that of basically doing a job. She needs to be useful and feel useful in order to both feel good about her self.
Also I get hints from her behavior that there is also a fear of rejection. That is to say a fear that if she is useless she will be thrown out. And my guess is that even her behavior toward the MC is predicated on that feeling. As in she does not want affection out of pity. She wants it to be deserved or not at all. She is simply to proud to accept anything else.
So no, I don't think she will turn into a BDSM character.