Yea, it's a female JD for sure. I have one myself with an oscar. They get along great, but the oscar is larger, and has always been larger, than the JD. I had a 4in male JD with the oscar when he/she was at 8inches, and the oscar got owned so I had to return the JD. Got a female JD (she's at ~7in now) and the oscar is now about 10in and they get along fine. Just make sure the tank is large enough, and you should be OK.
yeah 6" from nose to tip of tail and nice and plump. and she's been in the tank with the O since i got her at about 1.5 inches. the O's always been bigger and is now about 9 or 10 inch. he just chases the JD once in awhile after feeding. but shes got 2 caves to herself and seems fine.
all the pictures iv seen of JD's all the dorsal fins are one fin. if u look at the first pic of the larger ones i posted u can see mine has a gap in the middle of the fin making it 2 fins. has anyone seen this before? its been like this since i got it.
looks like my jack dempsey girl actually. Search jackdempsey on here and u will see posts of pictures of other members jacks. They arent hard to breed but they will ge aggressive when breeding.