There's actually tons of them already deployed.
https://www.google.com/search?q=ai+therapist
It mostly suffers from the old GPT issues. It can't talk truth, and it can't tell if it does or does not. Of course it has zero intended social skills .. but it read a lot of books (most of them), and it can act like someone who does.
I guess it could do over 50% of what real therapist would do .. ie. listen patiently and react meaningfully. But I doubt it could react well in the most important moments. And I wouldn't be surprised if it could spiral into right out recommending a suicide, as literature is full of that as well.