Welcome back to the STD forum. I'll try to help. The bottom line is that I doubt any STD is going on here. As you will recall, that was Dr. Hook's opinion when you asked many of the same questions on the forum last May. And since you and your partner are monogamous and you have been tested, it isn't possible that a new STD is involved.
There are many causes of vaginal bleeding, including bleeding after sex. STDs, including chlamydia, are among the causes, but in general STDs are less likely causes than numerous other conditions. One possibility, which could be STD related, comes back to your apparently shared HPV infection: certain HPV lesions of the cervix might bleed. Whatever the cause, bleeding often is triggered by sex, so that part of the history doesn't help much.
Any unexplained vaginal bleeding should be investigated, so your partner should see her health care provider about it, as you apparently are planning to do. Depending on what is found on examination, her doctor might test for certain STDs, but except for the possibility of an HPV related cervical problem, there is nothing in your story particularly suspicious for STD. I have no particular recommendations for her doctor. Any gynecologist knows more about the causes of vaginal bleeding than Dr. Hook or I do; STD experts don't generally deal with this sort of problem; gynecologists do.
Feel free to return to the forum to report her doctor's diagnosis, especially if it turns out to be STD related. But I doubt it will.
Regards-- HHH, MD