Yes, hair is linked to the soul. That is why people go grey as they get older, their connection from their soul to the physical world and their body is waning, so the power of the soul to be able to regulate the body's normal functions is decreasing hence their hair turns grey (unable to produce regular hormones). What actually happens is the soul gets further away from the body because we avoid our connection to this world. The more we avoid the further we are, makes sense right? That is why old people rarely do much, not because they are old, but they are old because they are 'less invested' in this planet. Some people are the exception, and they usually have more energy as a result (energy is basically the soul, or comes from it, the soul is an unlimited energy source it's just our bad choices take us away from it).

The hair being cut is simply an attempt for, say, britney spears to take away her femininity. This is because her image is strongly linked to what attracts people and attention to her. She cut her hair to defy that, basically.

Also, remember how when goku goes Super Saiyan his hair changes? ;) I think that's because it's a symbol of how our closer attachment to our soul can bring about blonder hair, but I'm not sure. The soul is sort've a gold blonde, so perhaps that is the symbol, when you cry and tap into your soul purely maybe it can manifest in physical changes like that.