Non-Crypto Trader with a question

I am not a crypto trader. I do have a friend who is, though it's not a close acquaintance. They said if I wanted to try, I could download trust wallet, coinbase wallet, then send them my Ethereum address from in Coinbase wallet, fund my account through Trust Wallet, and they would use my Ethereum address to "synchronize" our accounts so that whatever trades they made, I would make automatically with whatever money I wanted to put in. (Say, 500 bucks for instance).

To me, this sounds extremely shady. They aren't explaining how they would sync our accounts, what method/program they use, etc. However, the average online search says sending someone an Ethereum address is generally safe. I just don't see how they could use that sole information to do what they're saying. If so, by what method?

I initially saw this as a harmless way to have a glimpse into what trading in crypto is like. But now I'm starting to feel as if there is a method of phishing/scamming of which I'm not aware, and I don't want anyone with access to my personal/financial information for obvious reasons.

If someone could explain to me how this works in layman's terms (ELI5) or whether this is a setup to grift money and/or personal info, I'd appreciate it! They're very annoyed by all my questions, which is part of why I'm so skeptical. Seems like there would be no reason to hide what they're doing or how if it was safe and legitimate.

Anyway, let me know what I'm missing, if anything. Or confirm what my gut says — that this isn't a real thing, and someone is trying to see if they found a new mark.