Are her issues with negative God beliefs more pressing and important to resolve than loving and accepting herself? Would alternating sessions addressing these issues be a good idea?

That indeed would be a worthwhile plan because the two will complement one another and also facilitate accessing key things needing attention. So it will widen the scope of what can be taken on and worked through and will also hasten progress by spreading the benefits to a bit wider agenda that is self-reinforcing and will synergize with the issue of self-acceptance.