daughter is distant;possible drug problem

My 22 year old daughter has been living off her friends for the past 4 months. She has not contacted us for this whole time. She did not leave on bad terms. We phoned the police after she was missing for a month. I guess the word got around in her circle of friends and she phoned the police station and told them to let my husband and I know that she is not missing, she just chooses not to talk with us right now. I know that she smokes marijuana, but her friends are also known to use and sell cocaine and who knows what else. I see her car at a known drug dealer's house very often and many times not moving for days. He lives only 3 blocks away from our house. I I went to the house 2 times looking for my daughter, but both times he said that she wasn't there. I haven't approached the house for a month and a half now. I am off work right now with generalized axiety disorder and I have panic attacks. I don't know how I should be feeling towards my daughter and if I should continue trying to contact her. I've been trying to forget about her, but I feel like my insides are being ripped out.

I would fight and do everything I could find out, if it was my daughter. Would it be possible to take her to a clinic where she could get help?