I don't think you have a case for slander, but her constantly calling you, especially in the middle of the night, is harassment. You should report her to the police next time she does it and see about getting a restraining order. You may also want to consider getting a divorce.
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My colleague is correct that there is no case for defamation. She is not untruly smearing your name to others. She is saying mean stuff directly to you; which is not defamation (slander). I am also not sure there are grounds for an injunction, without actual fear of harm from her. Do you reasonably believe she will harm you?
However, I think there might be a case for stalking here. What you should do is not respond or feed the flames in any way. Do not text or call her. Keep a log of the times she calls and texts and keep copies of the texts, and phone records to doc the calls. If you can show enough of a pattern you may be able to get a cop to make an arrest. Most police officers are iffy on cyber-stalking stuff; so you may have to go to the next level and take it to your local State Attorney's Office and file a citizens complaint. Spell it out clearly and logically and provide copies of your supporting documentation and you may be able to get a prosecutor to issue a warrant or notice to appear, to start a prosecution.
However, I also agree with my colleague... Why aren't you getting a divorce? This is ridiculous. Divorce the guy and get a new phone and phone number and don't provide it to him/her. That should solve your issue. Please see a family law attorney in Coral Springs area. You need one. I am sorry for your situation.