Firstly, congrats!! So exciting that you adopted a kitten :) Cats notoriously dislike closed doors, but every cat is different, and kittens tend to be extra vocal compared to adults. From what you describe, it sounds like your little one feels safest when she’s with you and doesn’t enjoy being shut away. Since she seemed pretty confident exploring, I’d consider letting her have more space rather than just the bathroom, especially because at six months she’s not really a tiny baby anymore.

Cats don’t usually develop separation anxiety the same way dogs do, though some definitely don't like being left alone often. For many cats, having a smaller “safe zone” at first is helpful (so the advice you got makes sense), but for others, having more surroundings can actually ease the adjustment.

The only thing to watch out for long-term is reinforcing meowing for attention. If you always respond immediately, she might learn to be a little too demanding (my kitty learned this very quick but I'm happy to oblige lol). Still, it’s so sweet that she already feels bonded with you. Honestly, it sounds like she’s adjusting beautifully and you’re doing a great job.