Vicodin contains hydrocodone (opioid) and acetaminophen/paracetamol . 90 tablets in 2 days is a massive acetaminophen dose (close to 30 grams and 4 grams daily is the maximum) and would be toxic to the liver. If she is not feeling sick/appearing sick at this point, it is unlikely she took them all. However, if she has any nausea, vomiting and/or abdominal pain, get her to the emergency room and make sure the physicians know about the Vicodin. Even if she is feeling okay, if you find out she has taken them, she should be seen by a physician regardless.
Consider talking to her physician or your own as they should be able to assist you with treatment options or referral to a counselor/mental health professional.
You local health department would also know of area treatment options.
There may be Narcotics Anonymous (NA)
http://www.na.org/ meetings in your area. Anyone can attend open meetings and you may also find the associated group for family members. As well as someone at the meetings should know about services in your area.
edit: I have used she through this....apologies if that is a poor assumption on my part