AOC may not have monetary interest in TikTok, but she has generational interest (her national constituents are largely Millennials and younger). TikTok is mostly an artifact of Millennials and younger.
The fact remains it is a spying platform, and has been used to put surveillance on journalists and others.
National security interests are being weighed against generational-centered social platforms, and one would expect her to object.
Despite Trump/MTG being in the same corner