if you put your penis in the vagina without a condom, then there is a risk...however,the time frame of exposure is extremely minimal( 5 seconds)
you should be allright because of the short time frame, as for transmission to occur, normally the friction from intercourse is essential..
having said that, i suggest you do a hiv antibody test a 3 mths post exposure to be 100% sure..
i personally think you are allright as the lady claims she is clean,plus a VERY short time of exposure..