I think there are circumstances in which one's fundamental personality (which particularly in women is an external display of their emotional response to things/life/the universe in general), e.g. in the case of clinical depression or anxiety being overcome, or getting over something from one's past following counselling or some kind of epiphany.

But, I do think it's more common for people (particularly those with high social intelligence) to chance their behaviour and manner of speaking than their fundamental approach to life and all it brings. How long such a veneer can be kept up depends on either how much of a nutter the self-delusional sod or how intelligent the schemeing syren actually is.

I.E leopards can change their spots, but their probably still a leopard underneath!

Chris