It is possible you were smelling something else, not semen, such as her body fluids influenced by the food she ate (some food smells come out in the cervical mucus or the sweat glands at the top of the legs).
It's very important to note that it could also be a result of bacteria. There is a condition called bacterial vaginosis that has a characteristic strong smell from the vagina. You should urge her to go get checked by her doctor.
B.V. is not a sexually transmitted disease (don't worry!). The reason it is important to take seriously is that if a bacterial infection happens in the vagina and is not treated, it can (in the long term) cause pelvic inflammatory disease and in the worst case, infertility in the woman.
The doctor can do a swab to test, and if she has it, give her antibiotics for it.
This is not something she could get rid of with home remedies, if she has BV she needs antibiotics. Once when I had it, the doctor gave my husband the antibiotics at the same time, so he would not pass it back to me.
So, take her health seriously and urge her to get checked. Good luck.