It sounds to me like you handled the situation perfectly reasonably.
She proceeded to ask me all kinds of questions about how my life is.
As in, an unusual number of questions for someone reaching out as she was? I don't think you should feel any obligation to answer her questions, given that you're not really in touch and that you're involved in litigation with her son.
I wrote her back and told her I was glad she reached out, but I didn't want to put her in the middle. That her son was suing me and I am not comfortable sharing any part of my life right now. I hope she understands. I wished her well and said hopefully this will be over with soon.
Sounds like a kind and considerate response, and you give her a reasonable explanation for not opening up any further. If she is offended in any way by that response, it seems to me that's her problem, not yours. (I understand, of course, that it can hurt to think we've offended someone, even if we're confident we acted reasonably. So I can related to you having unpleasant feelings as you wonder whether she was just trying to be nice, but I think you're right in not acting on those feelings and opening up unnecessarily.)
I am proud of myself for not giving her any information, just in case she is fishing for him.
Good for you!
It is terrible not to trust.
I agree that it can feel terrible. But there are situations in which it makes sense not to trust. Or not to take on unnecessary risk by opening up. In those situations, I wouldn't say it's terrible not to trust. Not everyone can be trusted all of the time. It doesn't sound like you're passing any judgment on her, but you simply find yourself in a situation with her son where it really doesn't make much sense to share personal information with her.
I feel bad if she was just trying to be nice... .but since I am someone who over shares, it's best not to say anything... .right?
It sounds to me like ... .right
After all, you were polite and even kind in response. If she's upset in any way that you didn't share more personal information ... .well that would just confirm that you were right not to share!