Dilemma

So how would one go about telling a "new friend" (NF) that I think NF is full of shit?

Background:
Said NF is actually the wife of superdaddy's friend. She is a nice gal. In recent past, NF was addicted to pain pills. She used to get them from work or something or other. I never allowed myself to become a close friend with her. Being the good mother that I think I am, I kept my distance for a long time. As in almost 5 years. In recent past like 6 months or so, NF confided in me that she is trying to kick habit and make friends and learn to live life without narcotic glasses on. She is trying to learn to enjoy life with the boy being sober.

Not the immediate trusting person I am (had an addicted hubby in past who overdosed and passed away), I kept conversations to telephone; always keeping purse in eye contact with minimal cash and carry as I have been burned in past with ex. NF's hubby is superdaddy's best friend from school. Everyone knows she had a drug problem. They (NF and hubs) have many issue because of drug using and that is really their business. They have a boy now who is almost 3. My children adore him.

Problem:
Recently, they have been going to VBS with the kids and I. Her and I have been talking and haning out somewhat, I have became more of a friend, and less cautious. Monday things were well. The boy had so much fun at church. She was a class helper and seemed to enjoy herself as well. Tuesday, she watched the girls for me while I went to work. When I picked them up, I noticed that her eyes were like watery almost glassy. Like she was high. She got a shower and went to church with us. Well, she was nodding out in church like in the middle of everything. Like eating, and activities. We were painting and she nodded out. Nodding out as in like my ex-POS used to do on heroin. That is really the sickest thing I have ever witnessed in my life and quite frankly, I had flashbacks. I will never forget witnessing that. My stomach churned. I know her choice is not heroin. It is prescription vicoden, zanax, and zoma's. It was still really disturbing to witness. NF claimed it was being exhausted from being up early watching my kids, and going to bed late Monday.

Fast forward to Wednesday. NF called to ask if I can take her boy to church so she can finish cleaning her house. NF told me when she called that her and hubs got into a huge argument about money and her not working. She is a stay at home mom and like most places, the economy sucks and money is tight everywhere. To add to that, the house was messy from her having all the kids there for the day and when I got there to get them, we went right to church. I agreed to take the boy so she can clean up before he got home from work. Her eyes were still kind of watery/glassy.

How do I tell her I think she is full of shit about being exhausted and I think she is using? I think if her hubs was bitching about money and such, she probably took money from the bank for her fix like she has in past. It really isn't my business but I really believe in my heart she has her poker face on and I don't want to play poker. Lets face it, I am constantly busy with life, work, kids, single parenting, church, scouts and I don't nod out or have glassy eyes when I am exhausted. There is always something to do and never enough time. I don't want to be around someone who is using. Nor do I want my kids around it.