Farewell little Jenga  so sorry you lost her.

I think she has fin rot. But i am not sure

And by the way I hope Jenga has a good afterlife.

On one of the photos her body looks a tad unsymmetrical, which means that some internal infections are going on, either parasites or bacteria. And that's usually followed by swimming in an abnormal angle or even upside-down.
Sometimes the fins can look torn as well, but it's important NOT to focus on the smallest issue and treat the internal infection first. Usually you can easily treat both with medicated food and water treatment.

I would advise against using medications until water parameters are confirmed beyond a doubt. I know from personal experience that it can be disasterous to combine any kind of meds to unhealthy water conditions.

When my baby black moor Coal was suffering from ammonia poisoning he seemed to be very off balance as well as your Jenga. Torn/ragged fins are also a sign of this problem. Medications pushed him over the edge...a very sad experience.

The most common problem in all goldfish aquariums are usually poor water quality. In good water conditions with needs being met properly, it is usually harder to come across other problems such as disease and infection. If your water tests out perfectly, then and ONLY THEN should you try using medications I say.

thanks guys!!!