Is it health for ex-wife to text her ex-husband about her personal issues?

No, in my point of view, if they both does not have any contacts between them after they had separated means, then it will be good for ex-wife to text ex-husband about her personal issues.

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Many ex-couples actually get on better and are more friendly to each other than when they were married. Provided both are comfortable with the texting, and neither have a new partner that would be upset or annoyed, then there is nothing wrong.