Riven on paper would be great spell blade user, but since forever the only viable one was triforce, and that isn't viable at all for her. Sunderer looks like something that would fit her stat wise, but the 1.5 s cd is too high in light of her playstyle.. Since lichbane has now 2.5, and triforce scales base damage in combat, maybe lowering the spellblade cd on sunderer with haste/during longer combat is something worth looking at. I know it's doing alright, but it still feels kinda like it's only alternative for past triforce users, and nothing more (I think only gnar is sunderer user that didn't really build triforce before). This change could shift it more towards ability based fighters that rely on abilities and attacks weaved in between in quick succession.
Have you tried indexing hard on item haste to get the spellblade passive CD down? Could be exciting