Another way...Watch her kids at her house while she takes a nap. And if you can get something done for her while you watch the kids (make a meal, wash dishes, fold some laundry), she will not only get some rest, but also feel less stressed out after you leave.
I suffered postnatal depression after my twins where born. All i can recommend you do is ask your friend if you can help out looking after the baby whilst she speaks to a proffesional. It will be hard to broach the subject but it needs to be done. She needs to talk to a professional, she doesnt have to have tablets, i took antidepressants for just 4 months before being weened off over 2 weeks now i use a hypnosis cd every night. I wish you and your friend all the best and hope all is well soon. :)
send her anonamous gifts, subtle things. an extra christmas card or birthday present in the post. flowers delievered.
dont put any mysterious name or note just leave it.
small things brighten up people's day and it should work with your friend.good luck!
As someone who has had PPD on and off after my 2 pregnancies, I would say that one good way to help your friend is to be the one that she can talk to about anything, without being judgemental. All you have to do is be a sounding-board. She won't expect you to solve her problems, she just needs someone to vent on.