I have watched Angel about 5 times from beginning to end, and every time I wonder when did angel start like cordy for more than a friend?

At the end of the first season I believe, 'To Shanshu in LA' the first time Angel almost lost her. It was communicated quite clearly that this was when he realized just how much she means to him. It was the first of many times that he'd voiced needing her though his facial expressions said enough without words. When he says "I need you back" it looked like he was about to cry and at the end when she snaps back and looks at him his face lights up.

This extends to the Pylea storyline in his anxiousness to find a way there to find Cordelia who'd accidentally been sucked into a portal. Then in 'There's No Place Like Pertz Glirb' I recently picked up on a certain piece of dialogue that takes place just as Angel is able to overcome his demon self while facing Groo and is trying to make peace. Groo, however isn't having it and Cordy who is freaked over a vision she'd had about the fight comes between them.

Cordy: Stop, stop, don't hurt him. I love him!
Angel: You love me!?
Cordy: Not you dumbass! HIM! I love HIM *embraces Groo*.

Which she did she just didn't really recognize her feelings for him at that point or else was in serious denial. Angel looked totally crushed by that rejection.
He even tries to rebut:
"But she loves me too, right? As a friend, a coworker? Maybe love's too strong a word."

We get a glimpse in 'Eternity' that she did want to be with him
when she and Wesley get into a discussion of whether or not Angel had slept with Rebecca Lowell. Cordelia is convinced he couldn't have because of the curse but Wesley disagrees with that being an issue because:

"Its not gonna happen because the last time Angel was with Buffy. He achieved perfect happiness because it was with Buffy"

Cordelia falls back into her chair in a defeated manner like she'd tortured herself over that thought a dozen times. Wesley then had to add:

"He's certainly not going to find it with an actress"

and that gets a look from her that says he'd just shoved a verbal stake into her heart, like she felt that wasn't just aimed at Lowell but her as well.
Finally Wesley realized her reaction and it's connection to what he'd said so tries to make amends but the denial she remains in for the rest of the series/her life suggests the damage may have been done.
I wanted to punch Wesley for that. It irks me how even the characters on the show had at one time shown disrespect for the idea of Cangel. Gunn does it too in 'Heartthrob' when he points out that "the B word" was the love of Angel's life. That makes me cringe because I'm convinced that it's not true and who was Gunn to say that in the first place, he didn't know Angel then or Buffy.