Can someone really change?

So I called my grandma for her birthday on Sunday. She's a great lady and I really look up to her given that she's lived through so much and still has a great outlook on life. When I talked to her she told me two things.

1) My cousin Trevor's mother died about a month ago. She had had some kind of illness that was exaserbated by drinking alcohol. Of course I feel terrible for my cousin who is only a senior in college and has no lost both of his parents (My Uncle died while I was a senior in college from a severe heart attack). He's having to settle all the legal issues of her estate given that he's the only adult next of kin. I couldn't imagine going through that at any age but let alone before I'd even walked across the graduation stage into the real world.

2) My mother has quit drinking. She had gotten a DUI about a year and a few months ago and the punishment from the court included losing her driver's license and having to do some community service (all of which I think she should have done given that she could have killed someone!). She got involved at a church to perform her community service (scrubbing bathrooms and doing other things that if you knew my mother would be particularly painful). I suppose that the community service had some influence over her and she had been going to AA meetings.

All of this is good and I hope it does signify that she really is going to change and not drink again, but now the question comes up do I contact her now that I hear she's not drinking. I quit speaking to her over 2 years ago becuase of her behavior and the damage that it was causing to me and to other relationships in my life. On one hand I want to have the relationship with my mom mended, however, I'm not so excited about putting myself out there again with her. I had to go through a lot to resign myself to the fact that I may not talk to her again because she was hurting me.

Can someone really change? How do I know that she's changed for sure? Why wouldn't she contact me if she truly had changed?
These are just a few of the questions on my mind. I'm praying right now for wisdom to know what to do.