They have her say people may think she's an Alliance plant and she isn't... and then she asks a margrave in Maldraxxus about whether or not she is actually Forsaken because she was raised by Light (and the margave says "necromancy is necromancy")
The devs are full aware of the complaints about her and they are addressed in this questline. The Forsaken will always have doubts on her Alliance ties, hence why she is not the full leader, but the margrave makes it clear that Light and Death necromancy is the same (although we don't have many examples of Light Necromancy in lore, though the quest makes it seem like any magic posessing a corpse is necromancy... so the Life Zombies in WoD may be Necromancy as well)