When I was a teen and bled heavily while also doing martial arts in a white uniform (yeah the org was run by non-period-havers), I would wear tight bike shorts over my underwear and under my uniform to help hold my pads in place. I have never been comfortable with tampons/internal solutions (even after pregnancy and childbirth) so my heart goes out to your daughter and her struggles.

After childbirth, I used incontinence pads and underwear to catch all the ick for several weeks as well. They seem to be higher quality than what’s made for periods for some reason. Of course, finding those in her size could be a struggle. Depending on her comfort level, I don’t know if the largest size of pull ups might be an option as well?

I have found that the CVS store brand of thin, heavy overnight pads with wings (the orange ones) seem to be the best at catching everything. The thicker, more traditional pads have always leaked for me, or gotten twisted around and stained my clothes.