By definition any dependencies between user stories must mean they are not independent. Since dependencies can arise in both business and technical contexts, it follows that both the Product Owner and Development Team have a part to play in identifying them. This is one of the reasons why Product Backlog refinement should involve the whole Scrum Team.
It's fine to consider Product Backlog items in terms of priority. The important thing is not to confuse priority with order, because they are not necessarily the same thing. Lower priority items can rank above higher ones if they allow a more coherent Sprint Goal to be crafted, or if they allow important contingency to be be planned into high-risk sprints. In such cases priority may be expressed not in terms of an item's order but rather in terms of its value (e.g. MoSCoW priority), and any given sprint may contain a mix of differently valued items.