It could be hereditary or she could have received permanent damage. If she isn't gasping then she may be ok. You can go ahead and release her. Just keep an eye on her. She may end up needing a low stress housing arrangement so she doesn't get worked up.
Hi dark moon, I have a question regarding inflamed gills. Last week I bought a girl, and she came to me with it. Since then, she's been in 1sp a gallon AQ salt and a healing dose of Stress Coat. Problem is, 10 days since I bought her, her gill is still inflamed. From what I've read, any more than 10 days in AQ salt risks permanent damage. So, i noticed in your explanation of it, you said it could be hereditary. Does this mean that she's healthy, just has a puffy gill, or she'll die as soon as I take her out of salt? She isn't gasping anymore, just breathing normally, and the time she escaped(she's floating in my 10 gallon) she seemed fine, but it was only for maybe 15 minutes before I noticed. Sorry I babbled, thanks if you answer :)