GEN1226 Rav Aryeh of Bresslau (18th century) writes Teshuvos P’nei Aryeh ch. 98 that sinah is gross disgust and repulsion. It can be caused by a person’s behavior, or by his very different personality, that you cannot stand.   … this type of dislike is not a violation of harboring hatred in your heart.  This is the type of sinah that Yitzchak referred to when saying to Avimelech [this verse].  The term sinah refers here to the hatred of repulsion without wish to harm.   This may also be the type of hatred referred to when it is written “And Hashem saw that Leah was hated.” Genesis 29:31 Yaakov wished her no harm, but he wished to be somewhat distant from her. [The reason for this was because she cooperated with Lavan’s deceit. It is possible that this was repelling to Yaakov because he symbolized truth – “Grant truth to Yaakov.” [Micah 27:20 – AJL]   … Yaakov could not have actually hated her as a sinner for her role in Lavan’s fraud, because they would have then been forbidden to live together as husband and wife. Furthermore many Rishonim assert that you may not even hate a rasha [i.e., evildoer – AJL] until he has rejected your rebuke and continued sinning, which was not the case by Leah. However, that could be explained according to the Midrash that Yaakov called Leah a deceiver, the daughter of a deceiver. Leah responded that Yaakov, too, deceived his father, Yitzhak, when he pretended to be Esau. From this is seems that Yaakov did rebuke her, and she rejected his rebuke.]   CASTLE 513