My wife doesn”t dress tzniut. Open neckline, short skirt and the like. I have explained to her tens of times that she is doing wrong, to no avail. Question: may I divorce her lehatechila? It seems pretty straightforward from Shulhan Aruch that it is allowed and even recommendable to do so ( that a woman who is not keshera like bnot israel hatznuot it is a mitzva to divorce)
This is obviously a very sensitive question and would depend on the details of your situation. It is imperative that you get in contact with a Rav you trust and know well, who can guide you through this difficult issue.
It is very possible that if your wife understood how seriously you take this issue she would respond in kind. However this doesn’t mean she should be threatened with divorce. The message needs to be conveyed with compassion and tact. A respected Rabbinic figure can usually help a great deal. Divorce is the very last option after all other efforts have been completely exhausted. The fact that you told her tens of times is not sufficient, different tactics need to be used as well.
I wish you much hatzlacha to find a solution and have complete Shalom Bayit soon!