It's hard work in the first two years of teaching, trying to trim your life and exposure to present only the most authoritative and above-reproach face to the world. Shopping for work clothes for example becomes a major undertaking, as you have basically dress in purdah, gauging hem length, depth of neckline, etc in order not to be in any way alluring to your teenaged charges. As a 22 year old, this teacher may very well have overlooked the implications of being a teacher: that your life is basically no longer your own, that some parents will bay for blood if you so much as show a streak of humanity, and that some of your teenaged boys pupils will feel you are fair game because you are in front of them.
If we want to retain teachers in the profession, especially the young ones, is there any chance we could stop making teachers responsible for all the country's ills, and start actually attempting to instill some morality in our children at home, so that they are able to judge what is right and what is wrong at school without needing to be taught by nuns and robots? Children adequately brought up should be able to tell the difference between right and wrong by the age of 10 in most areas. If they don't, the PARENTS are the ones found wanting, not the teachers.
FWIW, I worked for 2 years at a very technologically advanced sec school: I always gave pupils my email address so that they could ask me questions re homework whenever they needed to. By extension, their parents had my email address. This facility was NEVER abused in any way by any of my pupils, or, surprisingly, by me.
The way things are at the moment (ie hate and abuse campaigns run online against teachers by pupils and parents) I would be more worried about this teacher than her pupils nor any standards of morality. In your place, I would mention it, just in case it is her student days site that she has forgotten to alter...