block her number
Maybe she feels like she needs your forgiveness or approval in order to have inner peace. I say don't give it to her. Now the shoe is on the other foot - you're in a position to make her suffer.
Perhaps she has mellowed with age. Similarly, she might have suffered from mental problems but now has a better handle on them. Just guesses.
Maybe she's come to regret what she did. People change, just takes longer for some.
That's a very difficult situation. I've never been in it personally, so I can only use any knowledge and wisdom I've gained through my own experiences to answer. I find that sometimes people change, better or worse, and that you have to each side of them into separate compartments. You'll have to decide if you can let go of your anger - righteous as it may be - and take the chance at having the mother you never got to have, if she's genuinely changed.
If she is still that way, then she's obviously not someone you would want to be around.
You can't expect to know what's in the head of a woman I've never met all I can do is guess