As I understand it, she started hallucinating well AFTER she started taking Zoloft, and it would therefore be reasonable to suspect that Zoloft was the cause - it is well documented that Zoloft can produce hallucinations in some people. That said, however, it is now a month since she came off Zoloft, and I would have expected that that these hallucinatory effects would have disappeared by now. There is little in the literature about how long hallucinatory effects may last - the duration is likely to be highly variable because of individual metabolism, rates of secretion and susceptibility. It is positive to note that the frequency of the hallucinations is decreasing (despite their reported intensity), which suggests that in all probability, the will disappear completely over time. I think that your best course of action is to continue the current protocol, and try to reassure your daughter that these will resolve in a few weeks.
You will find fully detailed information on Zoloft here.
I'm sorry that it is not possible to predicat accurately what is going to happen here, but to try to do so would be mere speculation, which would not really help you. It's best simply to follow the protocol she is on now and monitor events closely until you have a better idea about the direction in which things are going. It's still a bit early to be sure - just one month into the treatment regime - , but from what you say, she is progressing well.