 This is confirmed in the short story "Heorot", where Ms. Gard acknowledges that she is the Valkyrie Sigrun, though she notes that some of the legends are highly inaccurate.How many of her sister Valkyries are in the company, much less in the Mortal Realm, or what beings other than human mortals work for the company hasn't been revealed yet.Telling Dresden her True Name (or at least part of it) is a huge sign of trust on her part as there are a variety of hostile magics or abilities that can influence, control, harm or kill someone whose True Name was used in the spell.