I think the fact she'd been denied previously for roles that weren't The Doctor's daughter, made it even more obvious that she was only cast for tabloid inches.
Well, of course if that's what you're prejudiced to believe, that will reinforce that prejudice. But looking at it objectively, it's not at all uncommon for an actor to audition for multiple roles before getting picked for one; that's just a natural part of how auditions work. So there's no reason to read anything suspicious into it, unless you're actively looking for an excuse to do so.