There is really nothing you can do to prevent crossed beaks. I had one. I did have to trim her beak once in awhile. She couldn't eat pellets but did ok with crumbles. I had her for 3 years until one day when I was distracted a fox sneaked in and took her in the middle of the day. I did catch the fox and eliminated it. Gladys was very special.
These are what I used to trim her beak.
These are what I used to trim her beak.