Doctor Answers (1) on Mental health
The symptoms that you have mentioned that your friend is showing, like increased irritability, getting easily fatigued, anger outbursts, and somatic symptoms like aches, are highly suggestive of Post partum depression. Suffering from the 'blues' which is really an episode of depression, is a common phenomenon seen in women immediately after child birth.
Unattended, this episode can transform into frank depression which could be of varying degrees of severity, which seems to be the case in your friend.
I strongly recommned a Psychiatric consult for her at the earliest, for ignoring these symptoms would do more harm to her, and no good. Also, untreated her relationship with her spouse might also further deteriorate and she might reach a stage, where taking care of her baby would also become a big task.
A professional opinion, in person, is what I suggest.