I've got to agree w/ >>2 ... Has it come up in conversation where she's actually asked you to forgive her, try to understand her, etc...? If there was no forgiveness asked for, then maybe she's not looking for forgiveness... There's no point in telling someone you forgive them if they're not really that sorry or apologetic for what they've done... If she hasn't asked, then telling her you forgive her might come off as accusing her, and pointing fingers directly for what she did, causing uncomfortable feelings...

Now, if she's asked for you to forgive her, that's a whole different story... I think that for the most part, people can earn forgiveness for what they've done, and it sounds like she's at least tried in the latter few years to raise you like she should've earlier...