Ugh, having to deal with the side effects of steroids is always an adventure! It's going to be a two sided approach to resolve this.
The first side we'll tackle is her hunger. If you feed her kibble, invest in a slow feed bowl for cats (I promise they exist!), and break her food up into 4-5 smaller meals throughout the day. The slow feed bowl will make it more challenging to get the food, so she has to work at it longer and be more satisfied when she's done. Giving her smaller meals throughout the day will also help with that.
If she eats canned food, you will still want to spread the meals out to 4-5 a day. Take some plates and smear each meal across a plate, and freeze it. This way it'll take her much longer to lick the food up and it's like a slow feed bowl for canned food :)
Also invest in some very low calorie treats for right at bed time. In addition to giving her the last meal of the day right at bed time, toss like 10 of the treats around your room for her to hunt for over night. It should give her something to do and fill her belly a little so she's not screaming right away at 6am.
Now, to keep her away from the door. We get it - being hungry all the time sucks. But she also can't be damaging your door! But the more she practices the behavior, the worse it'll be to get her to stop. So we need to discourage this behavior starting ASAP.
There's a few options you can do, depending on how far you want to go. Depending on how big of the gap is under your door, you can wrap the bottom part of the door in tin foil (taped on) to discourage her from scratching. If that doesn't work, there is a motion sensor called Sssscat that when movement is sensed, makes a loud PSSSST noise and blows air. You can put that along your door so whenever she goes up to it, it'll go off and startle her. There's also a scat mat that you can lay across the doorway to she can't get to the door. These mats come in many shapes and sizes so you should be able to find one that works for your space. Both of these have websites you can look up to see the products in action.
I hope these tips can help!