It sounds like it may be beneficial for her to receive some professional help (like counseling). The professionals may help equip her with appropriate coping strategies when she is feeling stressed or experiencing any anxiety/depression.
Sometimes, when under stress, one may lose the ability to think rationally and act in a manner that is beyond one's control. It is best to find out what is causing this and intervene accordingly, before it progresses to something more serious.
I feel that what you could do is to provide a listening ear when she needs one. You are probably someone she could trust and turn to. Just be there for her when she needed some support would be good. Also, keep a lookout for any changes in behaviour (common symptoms of depression: http://scc.sg/eng/index.php/depression/ | common signs of stress: http://scc.sg/eng/index.php/stress/) and suggest options such as counseling to see if she is open to it.
For professional counselling service, you can consider Singapore Counselling Service: http://scc.sg/eng/index.php/counselling-services/
Hope your friend would feel better!
Read more