A few weeks back on GH, Nina learned that her brother Nathan was posing as "Ask Man Landers" to help Amy. Later, she got a curious call at Crimson. During these episodes, Nina was wearing a black cold shoulder sheath dress with an open back and ruffled sleeves. I wasn't able to find an exact match, but I found some similar options here, here, here, and here. Let me know in the comments if you know who designed her dress, and I'll update the post.

Nina Reeves's Black Cold Shoulder Dress with Open Back.