Always use a condom. but a one time unprotected sex exposure is low risk at around 1%. Plus, this was a friend that you'd probably have heard if she had HIV. Not an unknown person that you know nothing about. HIV is harder to get than people realize. At 4 weeks, you can take a 4th generation Duo test to be sure you didn't get it but would expect it to be negative.
Don't rely on symptoms to diagnose hiv. They are very vague. Just get a 4th gen test at one month time. Good luck