A couple of things I would say here:
Do make absolutely sure that the C diff is cleared. Get the best testing you can; protocol where I am to see if toxin is present is four stool tests on four consecutive days. Try to get the stool tests straight to the lab and keep them cold, it is really often missed in stool testing. If some c diff is surviving in there the steroids would help it to do so.
Iron supplements, not sure if she is taking oral iron but oral iron is controversial in UC and may even aggravate colon lining into a flare - if possible I would stay with the infusions and test zero oral iron - quite detailed paper on it here www.ncbi.nlm.nih.gov/pmc/articles/PMC3959949/
Can't help you on the biologic question as not had them myself.