I've flown with Siamese in cabin & really were not bad except yowled a bit during take off but that is kind of noisy anyway. and then just settled down. and I mean normally chatty Siamese.
If flying on the plane myself, I personally would fly the cat in cabin if possible.
But I have also flown cats in cargo and it was fine.
If flying her in cargo, I recommend either the Sky Kennel or Vari Kennel. size 100. Those are the sturdiest ones i know and approved by all airlines. They are both made by Petmate. Originally Sky Kennel was the one for flying, but since then they have become almost identical.
Get the carrier as much in advance as possible to give her a chance to get accustomed to it, so it is not something new and strange too. Leave it out open in the house somewhere that she usually hangs out. Put a blanket or cushion or something with her scent in in it. try to interest her in exploring it by tossing a treat in or a toy when you're playing with her. If you're lucky, she will check out the inside and even sometimes start lying in there. That would be great if she could already see it as a safe little den.
Get some crate liners, or puppy pads or diapers. There is a company called Dryfur that makes some good crate liners and their website also has a lot of tips about air travel for pets including examples of what kind of crates do and don't meeet IATA guidelines.
You will need food and water dishes that clip on to the inside of the door. It's unlikely the food one would be used for that flight but it is required. I think many sellers ship a double-dish with the crate. You also need LIVE ANIMAL stickers that go on the crate. But the airline should give you detailed info on all this.
You could try some practice runs by just going for a drive with the cat in the crate, then coming home and giving her a nice treat.
You might try spraying inside crate w/ Feliway. or simply using your own cat's pheromones by rubbing her cheek with a clean cloth then rubbing in the carrier. and keep repeating.
IF you decide to fly with her in cabin of course that means a different type of carrier since it must fit under the seat in front. Each airline has their own requirements for the dimensions. Some good ones are Sleepypod Air, Teafco ARGO makes some nice ones ( I have the Teafco ARGO Aero-pet) and I know a lot of people who use Sturdibag. Sherpa also has some good bags for in-cabin pets.
If flying in cabin, you will have to take the cat out of the carrier when you go through security. You put the carrier on the conveyer belt to go through the x ray machines and you carry the cat through the metal detector. It's a good idea to get the cat used to wearing a harness so that you have a way to more easily hang on to her.
Re getting a cat used to living indoors, I think a lot of what is important is providing an interesting environment. The AAFP has some links about environmental enrichment . Cat Wellness Care
Definitely check out the link from Ohio State University
If she likes to play, make sure to include some interactive play every day where she can mimic stalking and chasing and catching things. I love the wand/ lure/ fishing pole / whatever you call 'em type of toys and so do my Siamese cats.
You could also consider taking her for walks with a harness and leash. I had a cat I adopted who was very dominant and territorial, and had been used to being outside running the streets.... and he really wanted to go out and "patrol" but there is no way it was safe for him to be running around outside on his own here. So I got him accustomed to wearing a harness ( started by just putting it on , giving him a treat and taking it off. Then each day i left it on a bit longer, and did things like fed him when he had it on, or played with him with a wand toy, so he would focus on something else he enjoyed and not on the weird feeling of the harness. Then when it got to the point he could just run around the house with it on and not care, I attached the leash... which was another adjustment. but i put treats ahead of him so he would walk forward to get them -- or use a wand toy to attract him.
Anyway he was much happier getting his daily walk so he could rub scent marks on things and feel he was patrolling more of a territory.