I'm sorry your molly isn't well. Although NTD isn't limited to neon, I think it can effect danios, maybe some other fish as well.
I don't recall mollys being susceptible to it, but it sure sounds like your molly is showing symptoms of it. But aware, other fungal infections can have these same symptoms.
Can you post a pic? Maybe someone will be able to identify the symptoms.
Should it come down to that, and only you can be the best judge, Clove oil is said to be humane than freezing, but like Dojella, I've not had to do this.
There's a thread on the forum somewhere.
If I can find it, I'll edit this post and give you the link.
Edit:
preferred euthanasia method euthanasia