Hey Bro,
Its nothing worrying as I had seen it for quite sometime already! She did mention that it was only a hard crust birth mark that she is trying to get rid off and it is recovering now. I hope your post did not cause alarm and scared off her customer.
Next time ask her in private ma ? If you are really worry, then stop visiting her simple as that or engage in relative safer exercise for yourself (just go vanilla ML) ! Rather than asking in public and create unneccessary stress among bro here!