Miya's feelings towards Sota are definitely complicated and multifaceted. Earlier chapters showed that despite her abrasiveness she's much more comfortable around him than most other people. She also  knows that he's a good person, to the point of getting frustrated that he doesn't look after his own well-being like he should.
On the other hand, his overt persistence (especially since we've seen how creepy he can be when his nerves are acting up) even after being rejected is doubtlessly frustrating for her. And then there's the most obvious fact that he's an oblivious rival for the affections of her crush, who's been precious to her the entirety of her life. So of course, she can't help feeling jealous and resentful.
But if anything she seems to actively play up that resentment, probably because treating him as a "kinda sorta enemy" is easier than untangling her complex feelings towards everyone involved. I think part of her does feel an affection and appreciation for Sota, given her displays of jealousy and her subtle enjoyment of his praise. But it's buried under her fixation on the president and categorizing Sota as a rival. So even when she thinks she wants his attention aimed at someone else, she can't help but cling to him and his attention.