For anyone to be diagnosed as depressed they need to exhibit the symptoms for at least 2 weeks, nearly everyday. In my opinion it would be too soon to label her as depressed. It is possible she is going through a mood change or could be due to her hormonal imbalance and/or menopause.
Next Steps
Please try to get her to open up about her feelings. Too much exertion on the body can cause loss of attention and weakness. Sometimes when the mind cannot take a lot of thinking, the body reacts in the for of crying, especially in women. If you feel the problem is out of your hand and she fails to open up, please take her to your physician and take a call from there.
Health Tips
Please get her to open up. Best way would be to take her somewhere out (park or beach) somewhere airy.