How she doesn't have to touch the ground
1. She can use UpB twice, but in order to use it a second time, she has to jump after her first UpB, then she can use her second UpB
kind of like *on ground* UpB -> Double Jump -> UpB
But she can only use it once if you do it the "normal" way as in: Double Jump -> UpB, which is why you will see a lot of Bayonettas reserving their double jump.
2. She has a technique called jump cancel which allows her to cancel her jump into an UpB. After using this technique, she gets an additional jump. So she can do something like: *on ground* Normal jump -> UpB -> Jump Cancel UpB -> Additional Jump, resulting in getting her to higher places than usual. To give an idea, she can go to the top of Final destination by doing the example shown.
Her attacks in the air
1. Her sideB, has a characteristic where if it hits an opponent/object/etc, it can be used again (within 1 or 2 seconds) but no more than twice.
2. Many of her combos aren't true, but the player using her can adapt to their opponent's DI (Directional influence) to make it close to a true combo.
3. She doesn't have a limit to her aerial attacks, but has a limit on her aerial specials, as stated with her UpB and sideB
Setbacks
Although she can stay in the air for very long, the more her specials and Bullet art aerials (long hold aerials) are used, the more she gets lag when landing on the ground. To avoid this lag, players will tend to land on platforms, grab ledge, or Witch time (downB).
Final Comments: although she is an uncommon character and may be hard to understand, don't panic when you're at 150%. She can't kill. Actually, be happy when you're this high because the other player is probably frustrated and will throw out random Smash attacks, back airs, and witch times, until one lands since it's almost impossible to perform combos at such a high percent.