I don't see what so deep about April Ryan, at least in the first game. She's a well developed and thought out typical teenage girl. Yes its, much better than most principal characters in adventure games but its hardly spectacular. As for the second game, I couldn't bring myself to play that rubbish and gave up after two attempts.
It's not that she was super-deep, she was very well fleshed out and believable, also she managed to remain likable while being pretty cynical and pessimistic. I guess some of that was thanks to the voice actress.