If you immediately noticed it, and the penetration was very brief, your chances of having anything are very slim.
She doesn't seem worried most likely because she knows the chances of her getting anything are slim, too. IT's not because she already has every STD. CSWs use condoms to protect themselves from you, not the other way around. They don't care so much about you, but about protecting themselves and their livelihoods, and they aren't evil - they are just people trying to make money.
If you want to test, you can test for gonorrhea, chlamydia and NGU at 5 days. These will be a urine test or a swab test, and these are the most common.
You can test for syphilis at 6 weeks, and this is not that common.
You can test for HIV using a 4th generation DUO test at 28 days. This will probably be an oral swab. Even if you had full intercourse, the chances of you getting HIV from a female are very low.
You can get a blood test for herpes now, and again at 12 weeks. Make sure it's a type specific IgG blood test. Test now because you could already have it and not know it, and if you wait, you'll never know if it was a new infection or not. Don't let them do an IgM test - it's unreliable and shouldn't be done on anyone except newborns. Many countries, like the UK and Canada, don't like the blood tests, so don't be surprised if you run into problems getting this in one of those countries, if you live there. Chances of you getting herpes from a mostly-protected, brief encounter are also very low.
Washing after sex does nothing to prevent STDs.
I wouldn't worry about this if I were you, but test if it will ease your mind. If you are in a high Covid area, you might consider testing for that, though, in a week or two.