If this is a script that you will be shooting, personally, I don't think it really matters.
Close up on a computer screen is merely a camera direction, so again, if this is a shooting script that only you will be using then that's fine.
Personally, I would write it something like this.
INT. BEDROOM - NIGHT
Barb sits down at her computer. Eagerly turns on the monitor.
A chat window pops up on the screen. Bold text reads--
"Hello, how are you?"
Barb stares at the message for a moment. Contemplates what to write back.
Her fingers poke at the keys--
"I've had better."
Just an example, but something along those lines.
I wouldn't write any kind of camera direction in my script. It doesn't flow with my style and I'm not really a fan of it. To me, that's all personal preference that the director will take care of when shooting.