Instagram vs TikTok - which is worse for teens?

So my 15yo has both and I'm trying to understand which one I should actually worry about more. Instagram seems more about feeds and curated posts (which is its own mental health thing I get it) but TikTok's algorithm is insane and she's showing me videos that... I don't even know how they're recommending that to a 15yo? Neither platform has good age verification. Is this just the reality of being a teen now? Do I just let her use both and check in, or try to limit it? What are other parents doing?