How hard would it be to make someone fall in love with you? Someone who already loved you at some point? Not that hard was what Mircea thought when she woke up the next morning when she told Frey to get out if they weren't going to fuck.
Oh, how wrong she had thought!
If you still haven't gotten the gist, it was quite hard. Hence, there was a thin line drawn between love and hate, it was basic nature of creatures to hate something or someone if they loved it and that was not the case anymore.
What Mircea was perceiving was Frey hated her now more than ever, because of that night. It had been six days since then and they still hadn't as much as kissed let alone have sex.