There isn't much you can do at home except fir maybe trying to gently wash it and make sure it is dry. Thus sounds like it may be infected and you need the Vet to check it and she may need antibiotics. Does he offer Care Credit? I would assume this would be considered post op care and there would be no charge. That is how my Vet handles this. You would have to pay fir medications. You really need to give them a call for advice.
If there is something wrong with her incision that should be covered as a post-surgical check and the vet shouldn't charge you to examine the incision. It's up to him to get her through that surgery and she obviously isn't through it yet.
You MUST take her back to him, though, especially since you say it doesn't smell good. That could signify infection and this could be fatal to your dog, especially since her incision is still open enough to leak. PLEASE don't let lack of funds stop you from taking her in, her life really does depend on being seen by the vet.
Please keep us up to date on how she is doing and what the vet says.