Thanks for all the responses.
I made a few changes to Rosalina now. I didn't do the grab animations yet. I tested whether changing the grab offset would work for peach, but changing the ini file didn't do anything. For now I only changed the right frames for small Rosalina and normal big Rosalina. This way you can directly compare the right frames (new), with the left frames (old).
-I adjusted the width of the character, so that both versions - small and big - now have the same width, just like every other character, because otherwise if you are small and get a mushroom while standing close to a wall, the two pixels you grow would be inside the wall and make you glitch through the floor.
-I changed hitboxes for both, small and big Rosalina. For big Rosalina I also already changed the hitboxes for left frames, since they were really far off before, this way it is easier to compare right and left frames.
-For small Rosalina every frame has been changed. I made her face smoother and less clustered, made her arm a little bit longer, changed shading on her hair and dress, changed the shape of the dress slightly, changed position of her head because she looked a little crouched.
-Small and big Rosalinas' dress now looks different when she starts jumping than it does when falling/floating. Peach doesn't have that normally, but I thought it was more important for Rosalina due to the double jump. It looks weird when she suddenly gains velocity again due to a second jump, while there is no visual indication on her dress that she jumped again. Big Rosalina also is a little bit smaller when starting to jump (indicating crouch). And her arm no longer gets bigger in her jumping animation. (Maybe the animations are a little bit too subtle now, making her look a little more stiff while floating (floating animation may be too close to normal standing animation), but to me it looks okay)
-For all the frames where you see Rosalina from behind, I changed her hair to the typical shape of Rosalina's hair (the swing)
-I changed the world map sprites to look similar to the other Rosalina sprites instead of Peach sprites
-I changed her death effect to a similar style as peach's death effect.
http://www.mediafire.com/download/8na53 ... osalina.7z
Edit: Small changes to big Rosalina up climbing animation