Are these two sentences correct? If not, how can I rephrase them?

1. What possession of hers do you dislike the most? (hate is such a strong word)

2. (I really don’t see how this question is different from the first.)

Or, if you are not speaking of a material “thing,” then refer to it as a quirk or habit.

What habit of hers do you dislike the most?

i may have misinterpreted your question, but this is the correction of those sentences, if my interpretation is correct..

1 : what do you hate the most in her???

or; what is the thing about her that you hate the most????

2 : which thing of hers do you hate the most???

really hope this helps you….:)