From a site that you should be able to trust, Planned Parenthood, "can happen during sexual activity when bacteria from your partner’s genitals, anus, fingers, or sex toys gets pushed into your urethra. UTIs can also be caused by chlamydia, gonorrhea, or other organisms" and "having sex can lead to or worsen UTIs"
Now, while what you said was technically correct, you're simply trying to deflect the original poster's point that Clinton's UTI came from sex. It most definitely could have and you cannot deny that.
You really should think before you type.
https://www.plannedparenthood.org/learn/health-and-wellness/urinary-tract-infections-utis