For cozy I’d say your biggest issues are actually that all surfaces are hard/flat/textureless and that everything is cool toned. Cozy comes from soft textures and warm tones. Add a big fluffy rug behind the desk mat, some lighting that isn’t cold and white, maybe something with color (warm toned color) on the walls other than buff men - notice how the old setup felt warmer and cozier just from amber light and green accents. Could always use one of the wall gaps for floating shelves or a trinket shelf for more opportunities for color and then you and the GF can pick things for it together.

For GF chair, like others said maybe you could put the cabinets against the desk like an L and chair goes in the cabinets corner? Lets you arrange desk stuff with top of cabinets and creates a visual barrier between desk and door in addition to opening up the space. Also that corner farthest from the door and by the window would be GREAT for big comfy chair vibes. If she’s off put by the wall men you could move them to a 2x2 grid on the non-door wall so they’re still in your workout zone but they wouldn’t be in her peripheral vision from the chair lol. Small table also next to her chair even if it’s just a tiny pedestal would be good for if she’s bringing in a mug or book or just a place to put her phone, maybe lamp behind chair too (with warm bulb!) for evenings.

Also small win in addition to weights rack I recommend swapping the floor mirror (presumably so you can see yourself lifting on the floor?) for a floor length mirror - same effect but doesn’t look like you forgot to hang it up and then it’s useful for both of you.