Befriending Herion Addicts...

The thing of it is this:

1. I have a BIG heart.
2. I think everyone deserves a 2nd chance.
3. I have NO experience with herion or "the addicted".

Just by happenstance, a herion addict befriended me about 4 wks. ago.
I was out in my backyard and she kind of appeared out of nowhere... introduced herself. Told me her SAGA about herion and that she was 'clean' and had been for 2 mos... or so. I thought there was no harm in befriending her back, so I welcomed her as a friend.
I started helping her, as she was and had been in a wheelchair since she was 15 and she was 28. She'd been using for 8 years, at least 12 times a day. She told me she had been going to the "Methadone CLinic" down in Sugarhouse the last 2 years and that she was clean now...
She started lying to me. This should've been my 1st clue. I tried to believe that this was the truth, her lies and then realized it was all lies. Told Ron about it... he said to be wary. He said that she was probably using again... I thought this was a very calice sort of perspective and gave her the benefit of the doubt. I took her to Church with me and my girls. She lied to The Bishop right before my very eyes. I should've listened to Ron.
The day I met her I should've realized she was a junkie-liar. Then, she showed up to our house last weekend HIGHER than anyone I've ever known. Couldn't understand a WORD she was saying as it looked as if she'd been drooling the whole way over to our house. We were luckily on our way out, and so I had an excuse... "Sorry. We're just leaving." was what I said. She went, "bleahhhhhhhhhh.......bleahhhhhhhh........ drool." She wasn't even THERE!
So she's called me a BILLION times since that night and I haven't spoken to her, as I have been too mad and disappointed to talk to her. People have given me 2nd chances, and I sit here thinking. Am I being too harsh? Should I talk to her? What should I say? I just don't know what to do.