That's weird coming from a woman. Sex is sex and love is love, they are not quite the same thing. It is very easy to have sex and not be in love and it is also very easy to love someone and not have sex (mother and child for instance).
So the answer to your question is no, sex is not the true test of love.
If this girl only wanted sex, then she was definitely not in love with you.
Love means wanting to share your life with a person, it really has nothing to do with sex which is just a physical thing.