Betta blister/abscess/tumor?

[MJSpirals]

This is Gidget. She lives in my office tank. At first it looked like she was just getting a little chubby, then this bulge started to blossom. I treated her 5G tank with Betta Revive for a week, it did nothing to slow the growth. One day she was resting atop the filter and looked to be stuck there in her side. She just looked me in the eye and basically asked for help. The only thing I could think to do was see if I could drain the fluid. I put her in a small container with clean,non chlorinated water and a few drops of the revive. Kept her in the net, wore vinyl gloves and popped it was a sterile pin. She was annoyed but happily swam around the container. I brought her home and put her into a 3 G clean hospital tank with a heater and sponge filter. She was looking good, still happy, still eating, but that lump wasn’t going away. I kept up with the revive for another week. Still no improvement so I went big guns  with maricyn for a week. If anything she got worse. This is her today, day 15 of being at home. 
Does anyone have any ideas???

[Colu]

It could be a tumor or internal growth or a fluid filled  cyst it's difficult one if it's a tumor or growth antibiotic will have no effect if it's a cyst what I would do is Epsom salt baths 1 table spoon for 1 gallon 2-3 times a day for no more than 15 minutes the salt will help reduce any fluid buildup 

[MJSpirals]

Thank you! I did wonder if epsom baths would soothe if nothing else.