You can relax. That she "has been around" does not mean that she has an STD of any sort. In fact, the odds are that she does not. In addition, even if she was infected, most exposures to infected partners do not lead to infections. This is true for infections and any site but mouth to genital transmission is even less likely than genital transmission.
In addition, oral sex is an inefficient way to transmit STDs. Of the bacterial STDs only gonorrhea and nongonococcal urethritis (NGU) are transmitted through oral sex; chlamydia is not and without an obvious sore or lesion on your partner’s mouth, the chances of syphilis and herpes is likewise tiny. If you had gotten gonorrhea or NGU you will most likely develop symptoms of urethritis (penile infection) in the next day or two. Even if your partner had an STD (any STD and it is likely she did not), most exposures do not lead to infection. In your case, you had a single exposure; I would urge you not to worry. If you must, you could go to your local STD clinic or health care provider to be tested at this time.
Hope this helps. EWH
Thank you very much sir, that is a reassuring answer.