IMHO,
Leave this young woman alone so she can live her life in peace.

If you have difficulty doing it, then seek professional help to guide you.
If by any chance at all you are a monster to her? Contacting her in any way is not going to be pleasant for her. Respect her enough to let go...

You have a loving wife and children to consider.
Your wife is being short-changed by your obsession with this young lady. Why not give your wife the attention she deserves...

Therapy would help a great deal in working through this matter. Don't take any action until you have talked with an objective person about it.

I wish you luck in getting grounded in the present and not mired in the past,
Cap