If you still had sperm in your urethra, the fluid from your Cowper's gland could bring it up and deposit it into her vagina. 16th day after the period is not an unlikely day to get pregnant. Some women, day 14 is the one, but not every woman is on exactly the same schedule. If she ovulated on day 14, you would be in the clear by day 16 since the egg only lives for about 24 hours. But you have no way to know if she did.
I guess the thing to say is, she could get pregnant from this, and you two should start using condoms unless you want to be parents.
ADDITIONAL INFORMATION:
That was the 16th day after her period..(calculate from the first day of period)