I think it great that you want your cat to be indoors only. First, if she's not spayed, that's a huge step in solving the problem. One suggestion that I've heard about is having a water bottle handy when you open the door (coming or going). When she appears at the door you spritz her (or use any of the common techniques like an unpleasant noise). This should make her hesitant to rush for the door every time it's cracked open. Also, if she is the type to greet you at the door for petting when you come home, don't pet her right away. Walk all the way to the living room (or whatever room is a decent distance away) and then call her to you and pet her and maybe give her a treat. She will start to wait for you at that spot instead of being right next to the door. As for scratching at the door, you could try putting aluminum foil or double-sided sticky tape so it becomes unpleasant to scratch.
As for curbing her desire to stay in, that just takes time I think. If you can get her a cat tree (you may already have one), cat plants (like wheat grass), a kitty window perch, a bird feeder just outside the window that she can watch for entertainment, and lots of cat toys, because a cat that has been out in the great outdoors has so much stimuli that there's a chance she'll be bored inside. I hope you succeed in making her a house-only cat.