What apps can post videos on TikTok, without having the app in the phone ?

Hai ! I'm new to this community but I wanted to ask a question, my lil sister doesn't have my mother's professional TikTok account and neither has the app on my father's phone but still she managed to post videos (she is a kid and for obvious reasons we don't want her to expose herself on the internet), we checked but it's not from the phone gallery and she never had my mother's phone in hand so we are looking for other possibilities but don't know what to do anymore, she is autistic and is really good with phones but we can't find any other ways to post videos than the app directly or the phone gallery, has anyone any clue of any apps that could post videos ? Thank you in advance, we're doing this in order to protect her 🫶