Went and met poor little Jadey.
Hopped right onto my arm and practically begged me to take her home.
Zero manners, poops EVERYWHERE, smells like cigarette smoke, terrible, cheap diet, few toys.

. Could use a shower (Has never had one)
So what should I do? This is a much bigger bird than I’m used to... what is the best way to transition her and how do I get her cleaned up?
Speaking from several years as an Adoption Coordinator for a parrot rescue, I would suggested meeting with Jadey again at least a second time. A bird starved for attention may be very wonderful on the first visit, but not so friendly the next time.
If things go well the second visit and you are committed to bringing her home, obviously get the cage, perch and toys ordered. I would schedule a vet appointment and take her from the house direct to the vet for a full checkup, bloodwork panels including CBC and liver function, let them do the beak and nail grooming. Then it's just take her home and love, time and patience. Pick up a shower perch and let her sit on the perch in the shower and see how she responds to water, she may be a macaw that loves to play in water, otherwise, take your time gently mist if you have a handheld shower head. If she is on a crappy diet, just try offering her healthy pellets and lots of fresh food.
Once you have her in the house, take it easy so you do not overwhelm her with attention and such. Let her set the pace for interaction, if she wants lots of snuggles and affection, then give it to her, if not, work on target training with treats and building up the trust. But very often a macaw that picks their person, and if Jadey has decided you are her new parents, will go happily go home and adapts to your home as if she's been there forever. My Max was left at the shelter at 25 years of age, he decided I was his new mom and he came home with me right out of quarantine. And there was no settling in period, we joked he pretty much packed his bags and moved in like he owned the place

And still the same 4 years later!!
Same thing happened with my daughter, Victoria (riddick07 screen name here)... she bonded with a blue and gold, and if you look up photos and video, you would never guess that Titan had only just come home for most of those videos and pics.
Hope all goes well and Jadey has picked you as her new family and you have a wonderful transition with bringing her home!