There are indeed other conditions that can trigger behaviors similar to those w/ true schizophrenia. The Effexor is an antidepressant and it would take about 4+ weeks for some improvement in mood to manifest. The other medications being antipsychotic class medications ought to have fast acting properties, especially those in injectable form. The oral antipsychotic meds can show improvement in about 2 weeks in mood and agitation. Decrease of hallucinations or disorganized thinking can improve in 2-6+ weeks.
Things to consider would be whether or not there is a history of schizophrenia in her family as the illness starts to manifest in one's early 20's. Some conditions that can cause hallucinations/delusions (psychotic behavior) can be: Dehydration, Encephalitis (inflammatory brain disease), hypothyroidism, possibly organic brain cause i.e. tumor ( a CAT scan or MRI can show this) A spinal tap can look for brain viral causes for her behavior. Another cause may be that the psychotic symptoms are related to a bipolar disorder (mood spectrum conditions) rather than schizophrenia. There are multiple causes for hallucinations to manifest; even neurotoxicity.
Even though you're not able to obtain her medical records due to confidentiality, you may still be able to provide her physician with any additional information that you may have. You could also possibly ask for spinal tap test to be administered (if one had not been done already). Hyperadrenalism can be checked through blood work. Perhaps you may speak to the hospital's Patient Advocate (care advocate) to voice your concerns on this young woman's behalf.