What I'm getting from Donna this series, is that she's probably always thought she was a level better than those around her. When she split up with Carl in the first series; she assumed she'd be cutting herself free from this big weight, thought she'd really blossom and find something better. But now, in the second series, I think she's seeing that life isn't all that great, and perhaps the best thing to do a lot of the time is take what you can get. She might have always wondered if she'd have been better off away from Carl if she'd have stuck with him, but now she's probably thinking along the lines of...better off being stuck in a boring relationship with someone you can only half stand, then being left single for the rest of your life.
She thought she'd be off enjoying the high life, but in fact she's worse off than she ever was. On the surface, Karen and Louise might not seem like they're doing much better than Donna, but unlike Donna I think the other two don't particularly give too much thought to their lives. Okay, Louise has tried to better herself a little bit of late with those cock lollies, lol, but she does have that child like view of things, and seems to just go from one thing to the next, she doesn't really seem too fixated on the long term. Same with Karen really; she'd be perfectly happy with one night stands and hangovers for the rest of her life. Donna might have initially saw the appeal of that kind of lifestyle, but realized pretty early on it wasn't for her, it wouldn't take her where she wanted to go.
She does often come across as quite a mean spirited character though. For much of the second series she has been quite spiteful to Carl, trying to put him down to make herself feel better, perhaps to try and convince herself she's better off without him. But I do feel sorry for Donna, you really get that sense of being stuck in a rut with nowhere to go. I think that's made worse by the fact she's haunted by the fact she threw away the oppurtunity for some sort of future with Carl that may not have been ideal, but would have been good enough; and I think "good enough" is something Donna would gladly accept now.
