Hi
I don’t know what STI she has but I will answer this question assuming she has HIV.
It’s great that you used a condom and she is taking the medication as this will reduce the chance of HIV passing to you.
I can’t see how you would be at increased risk as it doesn’t sound like your penis came in contact with any vaginal fluid.
After a man ejaculates (cums) they recommend pulling out the penis before it becomes soft and holding onto the condom to make sure that semen does not spill. This makes sure that you don’t share any body fluids (vaginal fluid or semen).
It doesn’t matter if removed the condom when the penis was soft as long as the condom did not slip off while your penis was still in the vagina.
Have a look at our condom-broke page if you are ever in a situation where a condom does break or slips off. It provides information on what you can do to prevent HIV, pregnancy, STI testing etc…
If you are worried about what happened you could always talk to your health care professional about getting a HIV test.
Please leave a comment to let us know if this answers your question or if you need more information.
Health Nurse
For other readers, please feel free to leave a comment, or let us know if this was helpful.