Extend "freestanding" wall

[toma25]

Hello,
I am planning to install sliding doors in the hallway in front of a space where there is currently a small alcove for hanging clothes. However, I want to extend the wall on one side by 145mm and 70mm wide, which is highlighted in red in the image. I've been thinking about how to best extend this wall.
The black in the image is the existing wall, the red is the intended new wall, the blue represents the planned sliding doors.

The corners might get some bumps, so gypsum in the corners doesn't feel optimal. Can MDF be used? Can it be painted to achieve the same surface as gypsum?
Is it possible to use metal studs for such a short piece? If so, how?
The floor is oak parquet, the ceiling is concrete, with a ceiling height of 2475mm.
All suggestions are welcome.

 

[Bloink]

There should be no problems. Frame as usual, cover with plasterboard, and place metal corner beads on the outer corner. Personally, I would have chosen wooden studs if the sliding doors are to be attached to the frame.

 

[toma25]

Wooden frame to attach to, that sounds like a good plan. Are there metal corners that don't require special tools? no risk of warping with so little framing, there won't be a complete structure to stabilize.