Aw goslings are amazing! I have 3 myself.
I'm definitely going to give it a lot more time as well. She seems to be trying harder to do things she hasn't been able to do the past several days so that's an improvement. After her swim and once she is done preening and cleaning herself I put her in a towel and cuddle with her. Since I've been doing that she has seemed to perk up a bit too.
I also tried putting her in with newly hatched chicks but they just sort of waddled all over her so now I have her outside of their brooder but still next to them. She always seems happy when I see her. I put her outside with everyone else for a few hours every day and that also seems to help her morale. I suppose time, love and an hour or so of PT everyday should do the trick.