Wedding Dress Seam

As a general rule of thumb, altering a dress by more/less than 2 sizes is difficult and not advised because it can completely change the dress (and sometimes can be more costly than just buying a brand new dress). There isn’t a photo attached so it is hard to say what the issue is with the seam. If you’re not happy with it, I would speak to the seamstress and ask if there is any way to change/conceal it better. They may explain to you that it’s not possible, or perhaps there is more you can do. You won’t know until you ask.

Take it to another seamstress to fix it

Now I see it, I gotcha.

I imagine that your issue is that obviously the material is not continuous (i.e. you can see the seam) but after such a significant alteration I personally don’t think there is really much of a way to improve it.

Agreed. I think such a visible seam is to be expected when altering the dress by six sizes and am not sure it can be fixed much. I think its fair to have a conversation with the seamstress about what you don't like, but don't be surprised if she says its a result of such a drastic size alteration and isn't able to remedy it.