I'm not exactly sure when I first purchased the second account for my wife to play World of Warcraft. But I do know that she didn't hit 60 until well after The Burning Crusades was out. And since she generally only quests with me, I'm usually the one to show her where to go since I've done most of the quests already. She did have a paladin that she solo'ed through the Dranei area until about level 20, but that's about it for her solo career.
A lot of times when I have somebody else showing me around, I tend to remember the area/instance less. As much as I pay attention, things don't come together for me until I've (A) seen it a few times, or (B) had to do the research like looking it up on a map. I think (or at least hope) that a lot of people are like me and they almost go brain dead if somebody's leading them around, and especially if they think that's the only time they'll be doing that quest.
My wife's the same way. It's taken her awhile to remember where things are, mostly because she has me as a crutch so she can ask me about stuff whenever she wants. She can go make her Shadowcloth by herself, and she usually remembers where the bank is in Shatt. But with the less time /played she has, and using me as a crutch, she certainly doesn't remember as much.
Last night, we played the Beta for a bit. (We both got keys.) All of a sudden it dawned on her, "You don't know where you're going, do you? You've never done these quests before?" And when I answered in the negative, she was excited about that. We'd get to work together exploring new quests and areas. Not just me telling her where to go. She liked that. It was neat to hear the excitement in her voice. And come to think of it, it sounds like it will be fun.
The only question is: how do I get her to forsake all other hobbies so that we can level to 80 together uninterupted? Wow... I really need to get another hobby. lol.