One of the weirdest movies I've ever seen

At risk of giving more importance to the "storyline" than the film itself does, I'll make an attempt to address your specific questions:

When the doe takes the little girl to the berry bushes, she makes some important comments such as "brightly colored berries are often poison" and "when you die in a dream, you wake up". Next thing we see is her 16-year-old self first appearing catatonic but then waking up. So it seems the red berries did indeed kill her in her dream.

The older girl wakes up in the derelict ruin of what was once her house. Several rooms of the house are still intact, as is the moat. But time has definitely passed: note the cobwebs everywhere (including over her face), the rickety remaining footbridge from outside into the castle, and the fully grown tree overhanging the moat. A few things -such as her grandma- are frozen exactly as they were 100 years ago. (Yep, this is unrealistic: over 100 years un-embalmbed bodies don't rot? the fireplace doesn't age at all?) So long as she stays in the castle, she's still halfway in the "old times", as evidenced by her wearing old-style clothes (corset? laces?). But once she ventures across the footbridge, she's in modern France, has a fully modern persona, and wears modern clothes (including black nylons with a horrible run).

The psychological trauma of waking up in a completely different world was discussed earlier by the three good fairies. (It's even worse than they expected, because the meaning of and expectations of "age 16" have also changed significantly.) The good fairies have apparently done somethng (although I never figured out exactly what) to lessen the shock, but even so our understanding is it's barely tolerable.