It could e a male because of the mouth and stomach, but a male generally doesn't have that type of female-spotting....is it alone or are there other Jags or dominant fish?
Making sure she eats until she is bloated is a good start....don't over feed, but feed every few minutes until they stop eating AND there is enough left for bottom-feeders, omegas and sub-dominants , if community.
She/hes is a lot darker when first purchased,only had the black blotches down the sides not the bands you can see now.
There was another inch bigger jaguar in the same tank with no blotches or bands but was very dark and subordinate.I would of thought it was a male except for being bullied.
The other tank mate for now is a 25cm green terror who has been behaving.
The stomach was very sunken but is a bit better now in the photos,has been eating small amounts very fussy.