Please help!

One of my balloon mollies has been sick.

I put her in a 1.6 gallon tank, since my QT tank has 2 goldfish in it, and started treating her with Super Sulfa. The problem is she has stopped eating and I think it's because she's too stressed to be in such a small tank.

I cannot set up another tank, so my question is:

Can I put her back in the main tank and treat the whole tank??
I have other balloons, guppies, corys, one pleco and some fry in this tank.

Honestly, it would be so much easier for me

I did it last night. I rushed out to Target and got a 15 g rubbermaid container. It was a mess. I tried to borrow one of the filters from another tank, but it didnt stay still. i ended up borrowing one of my turtle's in-filter Whisper 40i, which i have to put back in the turtle's tank ASAP.

I'm off to my class now and will come back only after 2 pm (it's 7:20 am now). Then, I'll go to Walmart and will get another air stone (which my lovely cat broke last night!), a smaller in-filter and a heater.

Anything else I should add??

any other ideas? it looks like she has columnaris.