She's pretty neurotic but she's not the first person in there to apparently lose it and I doubt that she'll be the last.
It looks really stupid and irrational to us viewers and it's difficult to understand because we couldn't imagine reacting like that.
However, like Rylan says - it's impossible to know what it's like in there unless you've done it.
I know me and I know I couldn't do it - even if they were pretty normal, decent, nice folk in there too. With Bear, it must be like living in a perpetual frigging nightmare.