I think my hc is that she's very dominant and dislikes the idea of vulnerability with sexual partners save for a select few (in her case in the past: Don Quixote and Bari). She might occasionally have had sex with some of the lower Kindreds in Don Quixote's castle solely for sexual satiation (and joining Don Quixote for his own indulgences). So she doesn't really let anyone top her aside from those very few.
I think Sancho's still discovering a lot about herself and what she likes even now because she rarely did much exploration on her own besides sheer physically getting off with the partners she dominated, and following along with whatever the partners she's willing to be vulnerable with were into.
If she were to explore things for herself a little more with full awareness, I think she'd also find that she's got a bit of a breeding kink she's yet to acknowledge, even if she's indulged in Don Quixote's before. She'd know about it but not be willing to admit she's more into it than just indulging it because he wanted it. Might be more into power bottoming if she's willing to let herself loose a little more, too.