Normally, the photographer retains the image copyrights to a photograph, unless there is a contract where the model gets those rights. Of course I am guessing that there is nothing in writing.
As such, one can possibly make a complaint for intellectual property rights, but it would be a weak case. Allow me to explain why.
You allowed her to openly access the photos, which strongly presumes that you gave her the right to use the photos as she wanted. You also dated her, which would make any such claims without a written contract sound like a jilted lover's revenge suit based on rights given as a gift while/before you were dating (with no conditions/limitations in writing).
A cease and desist as well as a takedown demand letter under DMCA and other IP rights may be sent both to HER and the dating sites she is using them on. The websites are likely to comply without much question simply to avoid a suit. Whether or not she is intimidated by the letter to stop using the photos is up to her. An attorney can come up with a "broad brush" approach to the demand letter(s) to make it sound like there would be a case and it may scare her. So said letter (certified) is recommended.
However, there is hope that she would not call one's bluff, because in truth, the case itself would be very weak.
At least the good news is that most parties do get scared and stop using said images once they receive such a letter.
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