That's great that you bought her a trampoline. It's important to always give her an appropriate alternative to whatever inappropriate item or activity she is trying to access. The jumping is certainly sensory, so a trampoline is a great start. Tantrums and meltdowns are considered the same thing in terms of behavior therapy. It's a reaction to her not getting what she wants and she thinks if she carries on, she'll get it. ignoring the tantrum behavior is the best thing you can do. Just make sure there isn't anything around that can hurt her (sharp corners etc). just let her scream and don't say a word or even look at her. you can be next to her but physically turn away until she stops tantruming. Give her quick praise for calming down (nthing excessive) and then have her appropriately request an alternative activity that serves the same function as the one she wanted before.. If she wanted to jump on the bed, take her to the trampoline and have her ask for it (verbally, pointing, signing, PECS; whatever she is capable of). She will most likely tantrum again but just keep repeating the process. These behaviors dont go away quickly. It will take a lot of consistency and practice and time.

I would start with a good OT. They could help you determine if some of the behavior is sensory based.

Ignoring the behavior you don't want to see ia a good step. You also need to reinforce the behavior you DO want to see; this can be down through praise, high fives, little treats. A lot of kids on the spectrum have difficulty communicating, and that results in behaviors. A lot of 4 y.o. may try to argue or plead if they want to do/not do something they are told; your granddaughter may not have the language to do that. If you can get her behavior therapy, you'll get answera for her behavior more quickly.

There's a saying, "behavior is communication." Sometimes it just takes us grownups a while to crack the code.

the aggression is something you will have to both ignore and block. If she goes to bite you and hit you try to move away. the spitting is something you'll have to ignore. Don't react to any of the aggression; try to not even makes sounds bc that may be reinforcing the behavior. When I've worked with aggressive biters I make sure to wear long sleeves, even sweatshirt material to protect myself. give her a 2 or 5 minute warning to leave the bathroom and set a timer that she can see/hear. When the timer goes off, prompt her to leavethe bathroom to another activity. When she leaves the bathroom give her a gummy or piece of candy. reinforcing the good behaviors are just as important as ignoring the bad. You can do that with any activity that she had hard time with when it's over/ time to leave.

Thank you for replying to me. The only time we see her act out is when she is not getting her way. The day started great. I'm trying to let her have as much freedom in our house as I can as long as it is safe. She was locked out of everything at her house and locked in her room at times. I made her get out of the bathroom this morning and that is what started it. She hit me, spit, bit me so hard she drew blood. She calmed down and I was able to redirect her. How do you handle the hitting, spitting etc

My grandson is communicating with undesirable behavior. He parrots words without understanding. He also has a great professional team that works with him on behavior and communication. You're doing what they are telling us. We also try to determine if he sees the object of his attention as a need or want. It helps us determine whether to say no or just redirect his attention to something else. Then we bring up the issue to his psychologist if it's a real problem so she can work with us on it.