Your sister-in-law looks at you frequently as if she liked you or had feelings when you asked her she said she sees nothing in you so what was all the looking about then makes no sense to me?

maybe she has a secret interest in you and feels guilty admitting it so shes lies to you...and maybe she just thinks your fun to look at or thinks your a good listener...the world will never know you can only find out. Don't get too into it because its your sister in law...