that all sounds good to me.

deep box storage in the very back, for old school papers, out of season clothes... clothes rod for long things, second rod (or even 2 rods, one above the other) in front for shorter things, hooks in the front. does the closet have a swing door? you could put shoes on the back of the closet door, too.

@ninigret Unfortunately it's a bifold door because of it's proximity to another door. It's such a strange space, but thanks for the advice and reassurance!

IME, the back clothes rod gets ignored because it is impossible to crawl through the jungle of clothes on the front rod. Try a top and bottom rod all the way into the closet. Use a shallow valet rod to hold the few long dresses in the front. If it doesn't work for her, you can change it in a month or two. Good lighting, perhaps from $15 motion activated battery LED lights, will help enormously. If she has more than 6 feet of clothes to hang up, she may benefit from watching a Marie Kondo video or reading her book (libraries have many copies since it was a best seller).

For fun... The closet is about the size as a twin bed. Could you turn it into a sleeping nook and put a freestanding wardrobe in the bedroom proper? My girls have a built in bunkbed nook. It's cozy. If the room is big enough, the bedroom be like a living room/hang out space with a cute sleeping nook off of it.

You could look into a revolving closet system. I have no idea what it would cost but if affordable it could solve some issues.

https://www.richelieu.com/us/en/category/closet-and-storage/closet/parts-and-accessories/revolving-closet-system-large/1189499 

I should have mentioned the other important factor, which is half of the closet only has a height of about 5'10". From what I've read, that's not enough height for a double rod. I'll attempt to attach a photo. We ended up having to redo our entire HVAC system, and this was pretty much the only place to put the ductwork.

I like the idea of a double rod on the back wall (like ninigret shows). But I would add a shelf above. This shelf will be high enough that it isn't useful for everyday stuff, but very useful for out of season or rarely used items. In my closet, such a shelf hold my ski pants, paint clothes, and a tub of off-season (long underwear in the summer, shorts in the winter).

That leaves you with the side wall, about 4 feet long, maybe 8" deep? I like the idea of a shoe rack, and short rods (coming out from the wall) for dresses.

Can you replace the bifold door with two narrow hinged doors? That might give you some back of the door storage.

I'm curious to see the solution you end up with!

@sznns I actually looked at one of those! Unfortunately you have to have 4ft width for those to fit (and they are also around 2,000 dollars!!)

I posted before I saw your photo - that makes a HUGE difference!

I still see the possibility of hanging dresses on the right wall. I would also want more lighting, though once you hang clothes in the back, what you have may be sifficient.

If you put in horizontal rods across the front you'll end up never being able to get to the stuff that's deeper in. How about deep shelves with pull outs like they have for kitchen cabinets? Some hooks on the side walls for dresses.

We have a similar set up with a hall closet under the stairwell. It's definitely a tricky space. We hung a bar across the top and use baskets on the floor under the hanging section. In the back of the closet where it is hard to access we store off season items. In our case it's Christmas decorations. In your case, off season clothes would work well. We have hooks on the side walls for hats and other light items. Too bad you have a louvered door because we use the back of the door for storage.

Invest in a sturdy double garment rack -- hanging rods -- on wheels that she can roll in and out of her closet as needed. If that is 4' deep, then, in a 6' deep "room" you can build shelving -- about 2' deep -- at the far end of the closet.

https://www.amazon.com/Whitmor-Supreme-Garment-Rolling-Organizer/dp/B0055OC9OQ

I once stayed in a dorm room that had a narrow closet with a pullout rod arrangement so all clothes could be accessed. Your slanted ceiling may complicate that. It's been too long ago to recall the design that well. There are some pretty sturdy full-height pullouts made for kitchens, maybe that idea could be adapted for a closet.

If hanging needed a rod in forefront & store thing don't need often behind. Shelving if a lot of smaller items.

or

a cabinet with countertop builtin or a dresser.

Hope that helps