Zoloft is an SSRI (selective serotonin reuptake inhibitor), which increases serotonin. That improves mood, but more serotonin is not good for women sexually. Sometimes changing meds within that same class can have different side effects.
Wellbutrin (buproprion) is an antidepressant that increases dopamine. That can have the effect of improving libido, so sometimes adding it is helpful. In this situation, it might also be helpful to measure free testosterone and consider adding testosterone if it’s low.
If you consult with your physician and can't change your anti-depressant, you'll find some other ways to help with libido on our website.