Remus Lupin

You're sweet.

And as far as Tonks is concerned, she did help Arthur with Dean Thomas's paperwork, which was an enormous risk, and hasn't yet breathed a word, so we know she can keep a secret. She writes regularly to Sirius, which shows her sympathies. And she wants to be known by her Muggleborn father's last name, which also lets me know where her heart lies.

I'm not sure of everyone else's thoughts on the matter, but I think that if you trust her, Sirius trusts her, and Arthur's got a good feeling about her too, that's good enough for at least a trial interview I should think. If it doesn't look like she's up for it, you can back off now without too much danger.

And I'd rather break her into the group gently, in a controlled sort of way, rather than wait until an emergency arises, tell her the lot right then and there, and have to trust that she'd do the right thing.