We have similarities in our experiences. I also rapidly gained an astonishing amount of weight on Zoloft. It was the descent into obesity for me. My endocrinologist recommended the VSG to me and said that women my size (almost the same height, BMI, and pre-surgery weight as you, but a bit younger) with PCOS had benefited from it. Even without the PCOS I think there's prudence in obtaining better health now, before you reach morbid obesity and all the health problems associated with it. I had an extremely positive experience in Mexico having the VSG (mine was with Dr. Fernando Garcia) and in the 18 months since then have exceeded my goals. I think you'll be extremely happy with the results as well. Be aware that since you're starting at a lower BMI, you'll likely lose weight at a slower pace. It took me a year to lose what some do in a few months. The silver lining for me is that I've had no issues with loose skin or hair loss. I went from squeezing into a size 14 / XL to wearing a size 2 or 4 / XS.
I switched to a low dose of Wellbutrin a few months before surgery, which has thankfully helped to alleviate some of the depression and not caused me to gain weight. Many people taking a higher dosage have commented in reviews of the prescription that it helped them to lose weight by curbing their appetite, but unfortunately the higher dosage caused hair loss and anxiety in me when I took it, so I've stuck with the lowest dose.
If you continue to take Zoloft you might still experience weight frustrations even after surgery. There's a surgeon on YouTube named Dr. Matthew Weiner who has made several useful videos, including one about why people gain weight after having WLS. Medications were at the top of the list, with antidepressants being a notorious cause. Your surgeon might be able to offer some advice.
Best of luck to you!