The answer is probably: no. What other colleagues have advised is to have the student explain their arguments and responses, and then confront them if their understanding is not consistent with authorship. If you can't get a "confession" however, the detectors' false positive rate is just too high for proof. Then you can only fail them on the quality of content.
I cover detection in my "misconduct" essay – but not very deeply. The tools I have seen are disappointing, and the technology is in flux.
I am always sorry to hear this is happening. It's so draining 😞
https://sentientsyllabus.substack.com/p/generated-misconduct