My most recent adoptee (I guess it's been almost a year and a half now, he was 5ish when I got him) was like that. I don't know about where you live, but where we are there are not only tons of coyotes there is also a very fast-moving (like, typically 60-70 mph) road just 60' from the front door with all sorts of gravel trucks and such flying by. Outdoor cats on this stretch of road typically have very short lifespans.
So we kept "Mr Squirty" (plant sprayer bottle, set on stream not mist, just water in it) next to the door -- in fact there were days in the beginning when we kept a second Mr Squirty just *outside* the door, for when you were coming in. (We only needed this for the first few weeks, and very occasionally thereafter).
And I trained him to walk on harness and leash and took him outdoors 2x/day (only an option if you are somewhere reasonably quiet, without lots of pedestrian or dog traffic).
And, the big thing is, we have cat shelves at almost all the windows in the house; they have a raised "bridge" walkway across the kitchen at almost ceiling level; and when that wasn't enough for this particular cat I built him (and therefore my other cats too
) an outdoor "cat run" where they can go outside and bask in the sun or eat grass or bat at bugs. They've even caught an impressive number of mice and voles while out there! They REALLY like the run. I have posted pics of it on The Easy Garden (sister site); if you do a search here or there for posts with 'cat enclosure' authored by me, you can probably find the thread referenced. Even if you don't have as much room (or free time <g>), you can easily build something smaller that is still secure and enjoyable to the cat.
Mo pretty much stopped *regularly* trying to dart out the door after, I dunno, maybe 6 months or so. (The depths of winter helped considerably, LOL). There were still occasional incidents, including a few successful ones, all last spring. But I do not recall him having gotten out since maybe April, and frankly nowadays he does not really seem interested anymore. Occasionally he will sit inside the door and *watch* as you come in, but that's all.
All cats are different so your mileage may vary but it's worked for me, and the general approach (provide lots of window and high-up perches in the house, and controlled safe outdoors access) has worked for many other people, so it is probably your best bet. I think your odds are pretty good since she is still pretty young... just keep her from GETTING out, using Mr Squirty as needed, and she'll learn.
Good luck, have fun,
Pat
