Betta with swelling

We have a lovely pink female Betta that's been with us for almost a
year. We noticed she was starting to swell up in the chest area so I
quarantined her and gave her Epsom salts for constipation, what I've
been lead to believe is a common reason for swelling.

Well, that isn't the problem, when I changed the water in her tank I
noticed a lot of fecal matter. She continues to swell up though and is
now huge. It's evenly distributed and the fins that hand down from that
area seem to be pulling against her body because of it.

She still swims around and is eating and eliminating fine, but she
keeps swelling up like a balloon. I keep expecting to see it pop. Her
scales aren't popping out so I know it isn't dropsy.

Any help?

Klane