Seeing a picture would be easier to tell, but my DD has fine, thin, blonde hair and it's very similar. I definitely think that having it freshly trimmed is a big help - hers is still kept below her shoulders, so I consider it long, and she's had 4 haircuts, but I think there are still some baby hairs that need to even up! I know some girls can do the super long look and still look healthy and cute, but IMO hair does NOT look good if it's long but uneven, it just looks unhealthy, and it's really hard to achieve with fine hair (I have the same issue!).
As for what we do with her hair, she always has something done with it. If I just left her hair alone, it would be all in her face and just look gross. I do pigtails (either all of it - which needs some extra clips to get rid of flyaways so we don't do that often, or half-pigtails with just the top sections of hair), I do a little braid (she has a left part, so I go from there with a small section to her right and braid down, just to keep it out of her face), I do a small ponytail to the side or a small ponytail with just the very front section. I also do barrettes (just on the right, the section to keep out of her face), and lately she's wanted to try headbands, so we do those, but they don't look as great and we have to redo it often throughout the day. DD says that she wants her hair "like Mommy's" (I just wear it down, but style it), but she needs something in there or it just looks icky. She also can't do a full ponytail yet (we try sometimes, and even with a headband in, flyaway hairs just find their way out!), or really even a half-ponytail (although I can make it work with extra clips if that's what she really wants).
They do make mousse for kid's hair - we have this stuff by Circle of Friends, I think it smells like mango. I used to use it when DD still had baby curls (she'd probably have more still if her hair was shorter)... I'd use it to emphasize the curls and keep them from going flat. I don't use it right now because we don't need it, but I guess if I was doing her hair for something special I probably would.
Oh, and I never really brush her hair. We wash it at night during her bath, and in the morning since it's dry I wet it again and then comb it the way I want and then do whatever style for the day, and sometimes I now blowdry it if we're heading out soon and it's cold out, but I don't really brush it ever... when I have, I find that it doesn't really help anything, so I just stick with what's working for now.
Anyway, I know I rambled a bunch... I'm a big fan now of doing my DD's hair (and DD2 will someday have enough for me to style hers, too

) and I am, too, always looking for new ways to make it cute! (but definitely NOT toddlers &tiaras... I do NOT think that look is cute)