Welcome to the Forum. This risk of getting gonorrhea from analingus is roughly comparable to the risk of getting infected through cunnilingus and that risk is miniscule. Odds are that she did not have gonorrhea, and even if she did, analingus is a particularly inefficient means of acquiring infection. This topic was discussed extensively by Dr. Handsfield two days ago in a question answer that we discussed as he wrote it. Take a look, here's the link. It starts talking about chlamydial infection with oral sex but then goes on to discuss gonorrhea as well:
http://www.medhelp.org/posts/STDs/chlamydia-by-cunnilingus/show/1733963
Personally, after an exposure of this sort I would not worry at all and would not seek testing. If you need testing for your peace of mind (as opposed to meaningful risk), please do so but if you do, I predict the result will be a negative test.
I hope this comment is helpful, EWH