@MythicDraws
This was fun! ^^
Idle: Happy as Can Be
This theme would sound very upbeat and joyous, representing her excitable and kind personality! I think the xylophone would work, perhaps the flute as well. Maybe in the middle, a more mellow part plays, representing her tendency to blame herself if others are unhappy, but then it would go right back to what it was before.
Battle: Power of Friendship
I imagine this theme sounding upbeat as well, but perhaps it would be faster than the idle theme, with that more mellow part in said idle theme becoming a bit more prominent. Seeing as she is optimistic, I can see her not wanting to fight (hence the title), and would probably try to convince her opponent not to fight.
Boss: Don't Make Me Hurt You
With this one, most of the optimism would most likely be replaced with that mellow tune in the previous two. It would probably sound dramatic as well. Whoever is fighting her when this theme plays has to have done something truly horrible to end up in this position. Perhaps an excerpt of a sadder version of the idle theme could play at the end before it loops.