there may be more going here than the simplified 'she is a woman and therefore emotional'. Is it possible she suffers from depression? Or an undiagnosed medical condition such as hypothyroidism? If you want to calm her down try talking to her, ask her (kindly) if everything is alright with her, point out you have noticed she seems quite emotional lately and you are concerned, ask her what you can do to help her when she feels like this.
she certainly sounds over emotional...that must be hard work
because most women live closer to the true pulse of the universe than most men, and the universe is anything but calm and rational
hormones i guess