Which is one of the things he loves likes about her. He doesn't have to filter himself or pretend he's got a split personality disorder by referring to Angelus as a separate person. He can own his actions and not have to worry about her judging him for them or being utterly horrified. She knows that while that was him, he hadn't been in control of what he did while without the ability to discern good from bad and possessing a certain inclination towards evil.

He still felt that pull towards darkness — something else he didn't have to hide from her (she'd seen him get caught up in it, after all, when Darla was making a mess of everything) — but with a soul, he could fight back against it; ignore it. Angel didn't have to be that evil thing that made Angelus a legend if he didn't want to. And he very much didn't want to.

"I thought you went to your prom." Not the same thing, buddy.