Sitting

[HosseinM]

Consider
"I'm seeing her, she is sitting."
Does it mean
"I'm seeing her, she approached a chair then sat on. Now she has sat on the chair."
or
"I'm seeing her, since I saw her till now she had sat on the chair."
?
Also
Is "she is standing" like that?

[Josef Essberger]

"I'm seeing" her is not English.

Perhaps you mean: "I'm watching her"?

In that case:

"I'm watching here. She is sitting" means that at the present moment she is sat on the chair.

Otherwise you would say something like:

"I'm watching her. She has just sat down."