Welcome to our Forum. As you were already told on the HIV Prevention Community site, there is no risk of HIV infection from the exposure you describe, no matter who your partner was. Your partner indicated that she did not have HIV and most people do tell the truth. More importantly, there are no instances in which HIV has been acquired from receipt of oral sex. There is no reason for concern and no medical reason for HIV testing related to this encounter.
Just for completeness sake, I will point out that there is a small risk for infection with other STIs, specifically NGU (non-gonococcal urethritis) and gonorrhea. The risk of these infections is low but not zero. When person get them, they typically do develop symptoms (a penile discharge or burning on urination). If you choose to seek testing, both of these are easily tested for by an experienced clinician.
I hope my comments are helpful. EWH
Read my answer. That she was transexual makes no difference- still no risk. eWH
Even though he/she was a TS