"Yes, she is at home."
Translation:Ja, zij is thuis.
I've heard that in Dutch people prefer to specify the exact action like "hij staat" instead of "hij is". Taking that into account, can I express the same meaning in this case by "zij staat thuis" or "zij zit thuis"?
No not in this sentence, if I'm not mistaken these sentences including zit, staat, ligt, hangt etc. always include an action. Zij staat thuis makes no sense. Zij zit thuis is used a lot for people who are at home a lot for some reason e.g. unemployed or who are ill for a longer period of time, usually used for people of which you normally expect to have a job/go out, not for people after retirement.