I have been on Zoloft for 14 years and started when I was 19. It did not make me tired or withdrawn at all so it surprises me that she is having so much trouble with it. Then again, we are all different and have different reactions and symptoms. I would though think (and I am not a doctor) that it is more the trazadone that is causing the problems. Typically from what I have read the normal dose for maintenence anxiety control is 50mgs with adjustments being made my doctors as needed.
I agree with Paxiled a good psychiatrist is needed to review her medications and see if she really even needs any of them. I was put on it young not only for anxiety but severe panic attacks and zoloft saved my life. I was blessed to have a primary care doctor who recognized what I was feeling.
You appear to be saying either that the Zoloft isn't working, or that it has made her worse, which does happen with these meds particularly for someone that young. At that age, a good psychiatrist should be reluctant to prescribe meds, so I'm assuming her problems were so great she couldn't function and therapy hadn't worked. Now here's the thing -- Neither of these drugs are recommended for teenagers. No psychiatric drugs are, but they can be used if the situation warrants. But trazadone is very sedating, and Zoloft can be sedating or stimulating depending on the individual -- these drugs don't affect us all the same. Be careful here whatever you do -- Zoloft must be tapered off slowly, it can't be stopped abruptly for most people without side effects. I think you need to somehow talk to her and get her to a psychiatrist who knows meds well -- most don't and primary docs are worse -- and come up with a plan. And if she's not in therapy, she absolutely must include that if she ever hopes to overcome this, as drugs treat symptoms, not the underlying problem. Perhaps you can talk to her friends and see if they can have an impact on her, or get her on this site and we'll talk to her. Good luck.
How does you daughter feel on the Zoloft? Is it making her tired during the day? If so, she may need to change when she takes it. Maybe at night. It's really hard to say which med will work for her or if she even needs a change. She may need to adjust her Zoloft dose or like i said, take it at night. We all respond to these meds differently. If your daughter has you down on her Drs contact list you may be able to talk to him even though she is 18. Even though I'm much much older than your daughter I have my Mom down on my contact list and she is able to speak with my Dr. You can call to check.