Where do you think it is all supposed to go?
Some of it goes in her vagina and uterus and then comes back out.
Depending on what stage she is at in her monthly cycle, the sperm can get through the cervix and into the uterus and fallopian tubes. Most of the sperm eventually come back out due to gravity and muscle contractions.
You can read through this article on Go Ask Alice:
Go Ask Alice!: Semen drips out after sex