I will be of little help,
I'm in the same boat with Gracie Ruth. Boo loves to go outside and as soon as he hears me he'll run up to me and then run to the back door, then run back to me, etc until I make it to the door to let them out. Gracie has learned the meaning of the word and what to do from him, but only recently is starting to put 2 & 2 together, that outside equals pottying not just going out to play and terrorize Boo.
Gracie is 9 months old now and lately, she has been sort of, kind of looking in my general direction when she wants to go out. I've been diligent in watching her and am starting to see her posture change when she starts to think of going outside. I'll ask her and you can see the light bulb go on, "Outside? Yeah, that's it, that's what I want. Outside! Momma you are brilliant!"
Ok, so I added that last part, she doesn't really say that.
My only suggestion would be to take the treat outside and give it to her immediately after she potties. Don't wait until you come back in to give her the treat because then she thinks the treat is for coming in, not for pottying outside.