My GF is on ZOLFT 50 MG & now she don't have a drive. Is there any meds that can get her back in the mood?

My girlfriend and I been together for about 2 years now and we had a child together about 6 months ago. We were fu@king like jack rabbits before my daughter was born. My girlfriend now suffers from depression and was thought to be post-pardem depression but was diagnosed by physician as mild depression. She was prescribed ZOLOFT 50 MG tablets and her mood is a lot better and mood swings are more mellow but does not have much of a drive anymore. I am uming it is partially from the side effects from the ZOLOFT and part of maybe some hormonal changes with childbirth. Is there any prescription drugs or dietary supplements that can help counteract the side effects and get her drive back up? Please help!!