I am so deeply sorry for the loss of your son.
In my profession, we say that just about anything someone thinks, feels or does while grieving is within normal limits - but anything that causes a disruption in daily life needs professional assistance.
It sounds as if your daughter falls into this second category, and needs some help dealing with everything she is doing by way of individual counseling or medication from a psychiatrist.
To find either - first, if you have insurance, you can call the number on the back of your insurance card, and they will refer you to a few psychiatrists for medication or psychologists for therapy.
Secondly, you can look in your local yellow pages for names of Board Certified Psychiatrists in the "Physician" section (they list specialties alphabetically) or for a therapist under Psychologist (and PhD or PsyD) will be good. Call them and ask for a free 10-15 minutes, just to chat. Go in and see if you like them. GIve them a brief overview of what's going on and ask them how they would proceed - then see what works for you. Basically you want to be able to talk to them weekly and they give you feedback about good stuff you've done or any decisions that may not have worked right...
Another way to find people is to call your State Medical Association for a Psychiatrist or Psychological Association for a psychologist - they will give you referrals.
Finally - feel free to send me your city (and a few nearby cities) and other needs you have (Male/Female preference, etc...) and I can see what I can come up with.
Your best bet is a phone book - sometimes the ads tell you a little about people (mine does), so that may help.
Do be aware that she may refuse help altogether - she may need to run this through its natural course.