Spoilers for Twilight's identity.
Okay. In 8.11 'A Beautiful Sunset', Buffy and Twilight come face-to-face for the first time:
TWILIGHT: Do you know that I actually came here to talk? But there you were, going on about how hard it is for you, and, well... I just hate to see you cry.
So: Twilight "came here to talk", but instead of actually talking to Buffy, he decided to first beat up Satsu, and then Buffy herself instead.
And this is what happens the next time Twilight and Buffy come face to face, in 8.20 'After These Messages...We'll Be Right Back':
BUFFY: We were never really good at this. Lots of the other stuff, but not so much the talking stuff.
Looks like you're right, Buffy. Angel really isn't good at 'the talking stuff' when he's with you, is he? :-)
Incidentally, in 8.11 Twilight says he decided to attack Buffy instead of talking to her when he saw her crying... but I wonder if there's another interpretation? Maybe he saw her getting into a really close, intimate and emotional conversation with Satsu, and became overcome with jealousy? After all, it's not like pettiness is something Angel is totally immune to... :-)
The other thing of note in this scene in 8.20 has been commented on by plenty of other people, i'm sure, but it's probably worth putting it up here as well:
BUFFY: If you knew something about someone's past...and...future...would you tell them?
ANGEL: Probably not. You can't change a person's past. And just by telling them, you'll change their future into who knows what.
At the time, we all assumed Buffy was just talking about Willow here. But given that Angel is Twilight, is he also telling Buffy his own motivation? Assuming he's been informed that the 'Chosen' empowerment spell will bring disaster to the world - should he tell Buffy? He can't change her past; he can't make it that the spell never happened. And if he tells her about the forthcoming disaster, he'll "change her future into who knows what"... and perhaps make things worse instead of better. So he doesn't tell her.
(Of course, this isn't 'real' Angel: Buffy is dreaming. But Buffy's dreams have a habit of showing her the truth.)
There's another point to take away from this. Buffy takes dream-Angel's advice and doesn't tell Willow about how she went dark again and lived for 200 years until Buffy killed her. Instead, she comes up with the idea of running away to Tibet and getting everyone to strip away their power. That plan has been much-criticised; but I think it make a lot more sense if you think of it in terms of Buffy's guilt and worry about Willow. Divesting the Slayers of their power is a side-effect, or even a cover story: Buffy's real hope is that Willow will also give up her power, and not become Future Dark Willow, and not die at the hands of her best friend.
But in the end, when Willow does eventually find out the story - her reaction is not at all what Buffy feared. She takes it perfectly calmly. Like Sarah Connor, her watchword is clearly "No fate but what we make" rather than the idea that destiny cannot be cheated or escaped. So by following Angel's bad advice, Buffy nearly got all her friends killed. There's probably a lesson there. :-)
And on that note, I'll leave you with two contradictory bits of wisdom from Willow:
WILLOW: Vampires gain strength from each other. Slayers, ultimately, don't.
WILLOW: You're getting it from the girls, Buffy. Our girls. That's where all the power's coming from...you're sucking it from every Slayer who dies.