No orange tint on the belly.

i would say it is just a female. i don't see any markings/bars on the cheek area like you typically see on bluegill/green sunfish mix.

Is there a little blush margin on the opercular tab?

Yes, hard to see in the pic, but it is there.
Could it be a red ear sunfish?

Looks like RES to me. I'd think the red/Orange marking would be more prominent in a fish that size tho. May be a hybrid.

I have looked at the pictures numerous times and I am unsure. It looks like a RES but if it is the orange/red border is sure subdued. And if it is not RES it must be BG but the overall look looks like a RES. If it is a hybrid I would say it definitely would be RESxBG as I see no GSF influence at all.

I hope some of the experts chime in on the characteristics they see and what they think it is. I can't tell.

Edit: If I had to put money on it, I would bet RES................ or maybe hybrid RESxBG. Heck I don't know.

I would guess a BG X RES. Pect fin to long for BG and some tint on ocular flap. Pattern is mixed.