I don't think Dalia is going to get better. It's getting harder for her to come to the top for air and after she does, she goes down to the bottom, without control. She acts like it is so hard for her to breath and that she is suffering.
I'm sorry...just a quick question, when you look at her from the top are her scales looking like they are raised, kind of popping out like a pinecone?
You could either continue to wait and see what happens or put her to sleep humanely, it's your choice since we can't really see what the fish does and make a decision for you. Here's a good link to read:
No, her scales aren't raised. The main thing is her belly being swollen and she has not gotten rid of any waste this will be the third day. How long can she go without eating? I feel so awful for her. She is trying so hard to keep going. Her body seems to be to heavy for her to keep up.
I'm sorry to hear that, too. It is hard to lose fish people. Sometimes it just happens despite your best efforts to save them. You may never know exactly what happened to her either, unfortunately. I've had my own experiences that were similar. Good luck with your other fish!