I don't care about a person's past. What matters is how we get along right now. If she used to be an escort, fine with me as long as she is honest about it. Honesty and communication are important to me.
What's important to you? What others think about your gf and her past sex partners? You know girls want to explore different boys when they are young, which I think is a good way for them to find out with whom they are comptatible. Because marrying someone you are not compatible with, and spending the rest of your life with them, is not fun.
And after that, who cares what your platonic friend said your gf said? Maybe your platonic friend is not being honest.
I have a long time interest in psychology, specializing in relationship dynamics for 30 years.
(Please note, we give the best advice we can based on the information given in a post. For better advice, please include the age of all romantic partners.)