Hmm..I see your New to Peach. Well for now these are your bad habits I see you do alot
- Roll too much, you move into attacks and all. Try to get off that.
- You rush alot. Its not always good to do that.
- You need to get the grasp of FC (Float cancel) It makes Peach faster and your attacks too. Look up on Float canceling and how effective it can be. A way to practice it is to go to training mode and just go crazy with her FC. Try all her air attacks with FC at different heights.
Try to attack out of the shield more. Dont roll once you get attacked in your shield. When your enemy hits your shield, jump out of it to a N-air or Back air. Learn your FC tactics. Once you, You will see a change and speed in her. I'll be happy to help you if you have more question. but for now, try to work on what I said here.