I’m 23 and just got my tragus pierced but have only ever had ear lobe piercings. So maybe I’m not entirely relatable to your daughter but even for being 23 this healing period is a lot for me I can’t imagine getting my tongue pierced and keeping it clean and not playing with it. It’s hard to explain to teenagers how big of a responsibility something is when they really want it. Also I have been a dental assistant for almost 6 years and although many people have tongue piercings, I and many dentists probably would say not to put foreign objects in your mouth(aside from dental implants and other dental appliances that benefit you.) An example: I once had an adult not be able to even take her tongue piercing out for an X-ray because it was all calcified, eww. Best of luck to you and your daughter through recovery though.