I don't think seeing T1 again is at all "unfair" to T3. You need to do what you need to do to get the care that works for you. Like Scarlet said, if T3 has a problem that's her issue to deal with. And if it impacts the way she treats you or if she even tells you that she feels upset about it, that's probably a helpful sign that she might not be a very sturdy therapist after all.