My thought also is to be noncommittal. One kind message from her does not erase everything that happened and make her a good mom again. It will take a lot more than that. Like, for example, some genuine apologies.

You could look at those days she says she thought about you also as days that she did not reach out to you, did not try to be your mom again.

You could thank her for her kind words and see what she does next.

It will take a long time and a lot of consistent effort and interest and kindness on her part before you can (I think) begin to safely trust her.