regshoe

Good point! I think it was less about femininity and more just about it being brightly coloured and more showy than Lucy is comfortable with. Compare the trouble she goes to in finding a plain dress to wear at the fête:

In beholding this diaphanous and snowy mass, I well remember feeling myself to be a mere shadowy spot on a field of light; the courage was not in me to put on a transparent white dress [...] I had sought through a dozen shops till I lit upon a crape-like material of purple-gray—the colour, in short, of dun mist, lying on a moor in bloom.