Outside/inside cat transition inside only cat

Hi there. I recently moved and changed my cats from outside/inside cats to inside only. They have a large catio with grass and some flowers outside so that they aren't completely cut off from the world.
While my one cat seems to have adapted quite nicely, the other still howls in front of the doors at times. She's also recently started pulling out tufts of hair (not enough to leave bald spots) and has been bringing up hairballs. Some nights, it seems like she rarely sleeps prowling around inside.
Background info: They are on Hills Indoor cat food at the recommendation of my vet, I have spent a lot on toys which neither of them are interested in We have been in the new house for nearly 4 months, the cat experiencing this frustration is only 4.
Question: how long does it take cats to adapt to a change like this?
Any advice would be greatly appreciated!

Her behavior sounds not so much like she is stifled by being indoors but that she is insecure about her territory.  The prowling around at night suggests she is patrolling.  Sometime that can happen when they sense other cats outside--not the one she lives with, but perhaps other cats coming into your yard?  If you are aware of other cats in the neighborhood, try to keep an eye especially at night to see if they are coming onto your property, and keep 'em out!  Hope this helps.

I think once cats have a taste of the outside, they never forget it. Just cause we put cats in our houses doesn't mean all the wild isn't out of them. They don't understand that it's for their benefit that we keep them indoors to protect them. My cats try to bolt through the door every time we open it & they're usually near a window but inside is where they live & that's where they will stay. I'm sure your cat will mellow out over time, 4 months isn't really that long. She's still getting used to the new place as she's cruising around at night, it shouldn't bother you, they are nocturnal. Who know maybe she hears a mouse or something. My cats are always up & about at night, as they've caught like 3 mice since I've lived here.