You can feel safe Buying her all the platemail pieces as you won't find any better armor piece for her for quite a while, shield expert should be your go to then cleave then resilience, give her a 1-handed weapon and there's a quest in the warriors guild that you can do once you can access the place that a gives a really nice shield, if you want something better than the buckler there's a skeleton in the tomb were you found her ring that has a chance to drop iron shield which is nice
The enemy can be found in a small room inside one of those rooms with 3 ghosts in them