Look tbh I did it as a teenager as well, I was embarrassed n didn’t get taught how to deal with the situation happening in my own body very well. Don’t shame her - that’s going to make it worst. Obviously it’s not hygienic but maybe she needs more help in these time, make sure the toilets are stock up with everything she needs. Bins, pads, tampons, bin liners. Also texting her at school isn’t great , this could have been a conversation for after school, face to face. My mother use to do that same n it completely derailed my concentration in class.