First things first - I would encourage her to spend a day (or better, a week) with the computer OFF, and see what improvements she notices.
Second, she is going to have to learn ways of interacting that limit direct confrontation. My LO has a similar personality, though it's improved immensely now that he is very verbal. Sign language helped at that age, but he has very little patience for direct confrontation. So, you come up with playful and creative ways of getting them to do what you need.
For example, at that age, he would be filled with rage if I just said that it was time to leave the park. So, instead of even talking about leaving the park, I would scoop him up and "fly" him like an airplane, and talk about how we were going to go home and eat a snack, while he "flew" to the car. I'd never say that we were leaving, though, and by the time he figured it out, he was happily thinking about a snack at home.
To get him into his carseat, I would tickle him into sitting, then ask him, "Where's your nose? Do you see a doggy outside? Do you want your stuffed duck or this little singing toy?" etc., to distract him. If he pitched a fit, I did not force him into the seat
. Instead, I let him play on the seat nearby for a minute, then offered him a snack or something else, and said, "Ok, come sit in your seat and we'll have the raisins," and handed them to him while I buckled him in. Or something else. But forcing him once would mean I'd have to force him every time.
The key, for my son, at least, is avoiding showing any irritation in your voice, and never, ever force him to do things that are not absolutely necessary
. For us, that meant the only thing I ever really forced was 1 nebulizer treatment in an emergency situation. Anything else could be done differently, or we could wait a minute or two, or come up with a way to make it enjoyable. There were other things we started to force, then realized it wasn't a good idea, and we'd still have to work much harder the next 5 times to get him to go along with doing whatever it was, because he felt threatened.
I know many of my GD friends have often thought, "Why doesn't she just make
him do it?" at one time or another. But then they've witnessed the kind of blow-up that occurs if I do make that choice, and they realize that their own children recover quickly from being forced to do something, and mine does not.