i know that the real reason amber benson never played tara as ‘the first’ is because she was too busy, so they had cassie pretend to deliver her message instead, but my headcannon is that ‘the first’ couldn’t imitate tara because there was no darkness in her, and even ‘the first’ can’t appear to you as a dead person who’s that good, and kind, and pure. the first evil can’t touch her, even in death.