For the following questions you can answer using
"I have studied for 2 hours.
"I studied for 2 hours."
"I am studying for 2 hours."
First Question: What can she say at 4pm?
"I am studying for 2 hours." or "I have been studying for 2 hours"
Because she is describing the PAST, PRESENT & FUTURE she can use the PRESENT TENSE. Here the CONTINUOUS ASPECT because it is TEMPORARY, ACTIVITY focused. See Chapter 1 for more details. Would it be possible to use present perfect continuous